There are lots of arresting details in the book. We learn that the administration holds special animus for what it calls “D.O.J. women,” or women who work in the Justice Department. Wolff writes that after the white supremacist mayhem in Charlottesville, Va., Trump privately rationalized “why someone would be a member of the K.K.K.” The book recounts that after the political purge in Saudi Arabia, Trump boasted that he and Kushner engineered a coup: “We’ve put our man on top!”

But most of all, the book confirms what is already widely understood — not just that Trump is entirely unfit for the presidency, but that everyone around him knows it. One thread running through “Fire and Fury” is the way relatives, opportunists and officials try to manipulate and manage the president, and how they often fail. As Wolff wrote in a Hollywood Reporter essay based on the book, over the past year, the people around Trump, “all — 100 percent — came to believe he was incapable of functioning in his job.”

According to Wolff, Treasury Secretary Steven Mnuchin and Reince Priebus, the former chief of staff, called Trump an “idiot.” (So did the media mogul Rupert Murdoch, owner of Fox News, though he used an obscenity first.) Trump’s chief economic adviser, Gary Cohn, compares his boss’s intelligence to excrement. The national security adviser, H. R. McMaster, thinks he’s a “dope.” It has already been reported that Secretary of State Rex Tillerson called Trump a “moron,” which he has pointedly refused to deny.

And yet these people continue to either prop up or defend this sick travesty of a presidency. Wolff takes a few stabs at the motives of Trump insiders. Ivanka Trump apparently nurtured the ghastly dream of following her father into the presidency. Others, Wolff writes, told themselves that they could help protect America from the president they serve: The “mess that might do serious damage to the nation, and, by association, to your own brand, might be transcended if you were seen as the person, by dint of competence and professional behavior, taking control of it.”

This is a delusion as wild, in its own way, as Trump’s claim that the “Access Hollywood” tape was faked. Some of the military men trying to steady American foreign policy amid Trump’s whims and tantrums might be doing something quietly decent, sacrificing their reputations for the greater good. But most members of Trump’s campaign and administration are simply traitors. They are willing, out of some complex mix of ambition, resentment, cynicism and rationalization, to endanger all of our lives — all of our children’s lives — by refusing to tell the country what they know about the senescent fool who boasts of the size of his “nuclear button” on Twitter.