But hold up here for a sec—for the most devastating, most valuable and all-around best Trump book since he started running for president. In the vast Trump literature, this one is something new.

That’s because of the unprecedented access, and its pathos, which is because of the source—the president’s only niece, the 55-year-old daughter of his oldest brother, who died at 42 in 1981 in her estimation as a result of a pathological, decades-long destruction at the hands of his own twisted kin.

Mary Trump, to be sure, is a partisan (a registered Democrat who’s expressed public admiration for Hillary Clinton) with an ax to grind (she and her brother were all but excised from passed-down riches), and she writes, too, with palpable sadness and anger stemming from the long-ago loss of her father. The White House, meanwhile, predictably has dismissed her account as rife with “falsehoods” and “ridiculous, absurd allegations.” But she also holds a Ph.D. in psychological studies. And in these taut 211 pages, she puts us in new rooms, shows us new scenes with new details and lets us hear from members of the president’s nuclear family who have been conspicuously and obstinately mum. She is, after all, and by blood still, one of them—and “the only Trump,” as she puts it, “who is willing” to dish on what she calls “my malignantly dysfunctional family.”

Too Much and Never Enough (at least on its own) is not likely to hurt the president politically. (There’s plenty else at this point that’s doing that.) It’s not going to lead immediately to any legal jeopardy he doesn’t already face. It’s almost certainly not going to “take Donald down,” either, as she characterizes her impetus—first, she reveals, by having been foundationally helpful to a Pulitzer Prize-winning New York Times investigation, then by writing the rest of what she herself has written. But what this book does do is help us understand him, offering the most incisive rendering yet of why he is the way he is.

No matter what happens in November, historians will have to contend with the influences that forged the personality of one of the most consequential presidents ever—and in Mary Trump’s telling, the current occupant of the Oval Office, the man just shy of 63 million voters thought was the most preferable choice to lead their nation, is “a narcissist” whose “pathologies are so complex and his behaviors so often inexplicable that coming up with an accurate and comprehensive diagnosis would require a full battery of psychological and neuropsychological tests that he’ll never sit for,” whose “deep-seated insecurities have created in him a black hole of need that constantly requires the light of compliments that disappears as soon as he’s soaked it in.” She says he is “a petty, pathetic, little man.” She says he is “ignorant” and “incapable” and “lost in his own delusional spin.” She says deep down he “knows he has never been loved.” She says his reelection “would be the end of American democracy.”

I asked Trump biographers—people who’ve spent extended periods of their lives attempting to plumb his psyche—what they thought of her book.

Michael D’Antonio told me he found it “chilling.”

And Tim O’Brien? He believes it’ll be “indelible.”

“There were a lot of mob movies before ‘The Godfather,’ but ‘The Godfather’ gave us a very specific understanding of being in a mob family because it was this rich, detailed, inside account of how a family dysfunctioned together,” he said. “There was nothing new in ‘The Godfather’ about how mobsters rolled, but the portrait it painted was so searing and rich and authentic that it defined our understanding of a criminal family. And, yes, there have been other books about the Trump family—Wayne’s, mine, Gwenda’s—but none of us captured his family life in the way that she has.” O’Brien predicted Mary Trump’s work will have “a seismic imprint.” “It gives,” he said, “the deepest understanding of his family dynamics that anyone has provided, and how that shapes his psychosis, and why he’s such a dangerous leader.”

I was especially interested in the book because of a story I wrote in 2017. It was about the president’s mother—and why he had talked about her so much less than he had talked about his father.

Here’s how I started it:

“When Donald Trump moved into the Oval Office in January, he placed on the table behind the Resolute Desk a single family photo—of Fred Trump, his father. Sometime in the spring, White House communications director Hope Hicks told me recently, the president added one of his mother, Mary Trump. When, exactly, and why, Hicks couldn’t or wouldn’t say.“

On the fourth page of her book, this Mary Trump supplies the answer. She visited the White House the first week of April of that year, invited to a dinner to celebrate the birthdays of the president’s sisters, Maryanne (who was turning 80) and Elizabeth (75). The gathered clan entered the Oval.

“Maryanne,” the president said, “isn’t that a great picture of Dad?”

“Maybe,” she responded, “you should have a picture of Mom, too.”

“That’s a great idea,” the president declared—“as though,” writes Mary Trump, “it had never occurred to him.”

Reporting in 2017, I had tried to zero in on a distinct window of time when Donald Trump was a toddler, considering it not only an important moment for the purposes of my story but potentially one of the most important moments in the totality of his life. He was born in 1946, and his little brother, Robert, arrived two years later, their mother’s fifth and final child—final because she suffered severe complications after the birth: hemorrhaging, an emergency hysterectomy, an abdominal infection and a series of subsequent surgeries. She almost died. It took many months for her to recover and in some ways she never did.

I was cautious in how I treated this because psychologists I talked to were cautious in how they talked about it. They steered clear of family specifics, sticking instead to what’s known about the salience of a mother’s love for any child at that critical, formative age, and the potential psychological havoc of the lack of it.

In this book, Mary Trump has no such restraints.

The first sentence of the first chapter is this: “Daddy, Mom’s bleeding!”—a 12-year-old Maryanne wailing for help upon finding her disoriented mother on a blood-covered floor in one of the upstairs bathrooms in the Trumps’ big house in Queens. “For the next six months, Mary was into and out of the hospital,” she writes, and the “long-term implications” included “severe osteoporosis from the sudden loss of estrogen” and “excruciating pain from spontaneous fractures to her ever-thinning bones.” This exacerbated what was her somewhat stony nature to begin with: “… she was the kind of mother who used her children to comfort herself rather than comforting them. She attended to them when it was convenient for her, not when they needed her to. Often unstable and needy, prone to self-pity and flights of martyrdom, she often put herself first.”

She was “emotionally and physically absent,” she writes.

“The five kids,” she says, “were essentially motherless.”

Similarly unsparing are her descriptions of the president’s father. The book actually reads at times like a portrait principally of him, sketching Fred Trump as a callous, sneering, domineering, lying, cheating, vindictive, workaholic bigot. (He didn’t rent apartments to die Schwarze, which is how he referred to Black people, employing his first language of German. He also frequently used the phrase “Jew me down,” a pejorative term for haggling for a lower price.) He was in the end, in the words of Mary Trump, a “torturer,” “an iron-fisted autocrat,” “a high-functioning sociopath” who equated kindness with weakness and favored his second son at the disastrous expense of his four other children—particularly his namesake, Fred Jr., or Freddy, who “wasn’t who he wanted him to be” and was “dismantled” because of it.

She reveals as well by far the most intimate, even poignant glimpses at his late-in-life Alzheimer’s, describing a wig-wearing husk, coming downstairs in the evenings in “a fresh dress shirt and tie but no pants, just his boxers, socks and dress shoes,” asking what’s for dinner over and over, steadily forgetting the names and faces of everybody in his family—everybody, evidently, except Donald. “I don’t know if he remembered Dad,” Mary Trump writes, “because I never once heard him mention my father in the years after his death.”

“Fred,” she writes, “dismantled his oldest son by devaluing and degrading every aspect of his personality and his natural abilities until all that was left was self-recrimination and a desperate need to please a man who had no use for him,” she continues. “Fred destroyed Donald, too, but not by snuffing him out as he did Freddy; instead, he short-circuited Donald’s ability to develop and experience the entire spectrum of human emotion. By limiting Donald’s access to his own feelings and rendering many of them unacceptable, Fred perverted his son’s perception of the world and damaged his ability to live in it.”

The upshot, in her judgment: “Having been abandoned by his mother for at least a year, and having his father fail not only to meet his needs but to make him feel safe or loved, valued or mirrored, Donald suffered deprivations that would scar him for life,” leading to “displays of narcissism, bullying, grandiosity,” she concludes. “The rigid personality he developed as a result was a suit of armor that often protected him against pain and loss.”

She calls her uncle—the 45th president of the United States—“an epic tragedy of parental failure.”

A few years back, on a reporting trip to New York, I rode the subway out to the end of the F line in Queens and walked the half a mile to Jamaica Estates to take a look at what in the book is dubbed “the House”—the more-than-4,000-square-foot, 23-room, red-brick manse, set showily atop a hill, the biggest home on the block.

Inside, it was “formal,” “stiff,” “staid” and “cold,” friends of Fred Jr. have told me, recollections Mary Trump confirms. “The House,” she writes, capitalizing it like this throughout, giving it a special, sort of sinister air, “seemed to grow colder as I got older.”

She takes us in, past the neglected cement slab of a porch, into the library with studio family photos on the shelves but no books, down into the basement with fluorescent lights and black-and-white tile, “an old upright piano that stood largely ignored because it was so badly out of tune it wasn’t even worth playing,” and “my grandfather’s life-sized wooden Indian chief statues that were lined up against the far wall like sarcophagi,” as she describes.

“When I was down there by myself,” she writes, in a quiet kind of interlude midway through the text, “the basement—half illuminated, the wooden Indians standing sentinel in the shadows—became a weirdly exotic place. Across from the stairs, a huge mahogany bar, fully stocked with barstools, dusty glasses, and a working sink but no alcohol, had been built in the corner—an anomaly in a house built by a man who didn’t drink. A large oil painting of a black singer with beautiful, full lips and generous, swaying hips hung on the wall behind it. Wearing a curve-hugging gold-and-yellow dress with ruffles, she stood at the microphone, mouth open, hand extended. A jazz band made up entirely of black men dressed in white dinner jackets and black bow ties played behind her. The brasses glowed, the woodwinds glistened. The clarinetist, a sparkle in his eyes, looked straight out at me. I would stand behind the bar, towel slung over my shoulder, whipping up drinks for my imaginary customers. Or I would sit on one of the barstools, the only patron, dreaming myself inside that painting.”

It’s these types of keen peeks into private places that give this book its oomph.

We’re in the House.

We see Freddy dump a bowl of mashed potatoes on the head of a seven-year-old Donald. We see Donald hide from Robert his favorite Tonka truck toys. We see Robert kick a hole in a door.

We see their restive, insomniac mother, wandering “at all hours like a soundless wraith,” her children sometimes finding her come morning “unconscious in unexpected places.”

We see Fred chide Freddy without mercy, mocking him for wanting a pet, for playing a practical joke—for saying he is sorry. We see him deputize Donald in the degradation. “You know,” the second son tells the first, “Dad’s really sick of you wasting your life”—at a time when Freddy was a pilot in his 20s for TWA, having chosen to not follow in his father’s footsteps in the real estate business, and Donald was barely out of military school. “Dad’s right about you; you’re nothing but a glorified bus driver,” Donald says. “He says he’s embarrassed by you,” Donald says. “Donald,” his father says to Freddy, “is worth 10 of you.”

We see Freddy’s drinking get worse. We see Fred tell him to simply stop. “Just give it a quarter of a turn on the mental carburetor.”

We see family members gather at the House but not at the hospital the day of his death. We see Donald leave to go to a movie.

We’re in the House, “colder still,” for Thanksgiving a couple months later, and we see Robert put a hand on Mary Trump’s shoulder and point to her new, month-old cousin, Ivanka, asleep in a crib. “See,” he says, “that’s how it works.”

“I understood the point he was trying to make, but it felt as though it was on the tip of his tongue to say, ‘Out with the old, in with the new,’” she writes. “At least he had tried. Fred and Donald didn’t act as if anything was different. Their son and brother was dead, but they discussed New York politics and deals and ugly women, just as they always had.”

And we listen in as they try to mostly erase her from the estate after Fred’s death in 1999.

“As far as your grandfather was concerned, dead is dead,” Robert says. “He only cared about his living children.”

“Do you know what your father was worth when he died?” her grandmother tells her. “A whole lot of nothing.”

Now, in the middle of this grim and pitiless summer, in the last year of the first term of the presidency of Donald Trump, here is this book by his niece.

She presents her uncle as fundamentally and profoundly incapable of an empathetic or merely effective response to the challenges of this or any other era. “Donald,” she concludes, “withdraws to his comfort zones—Twitter, Fox News—casting blame from afar, protected by a figurative or literal bunker. He rants about the weakness of others even as he demonstrates his own. But he can never escape the fact that he is and always will be a terrified little boy.”