The essence of irony, Henry Fowler wrote in “A Dictionary of Modern English Usage,” is that it “postulates a double audience” — one that’s in on the joke, and another that isn’t. The title of Philip Rucker and Carol Leonnig’s new book, “A Very Stable Genius,” is thus savvy marketing. It’s possible to imagine both Donald J. Trump’s detractors and his admirers eagerly grasping a copy.

The admirers will not make it past the table of contents. Among the chapter titles: “Unhinged,” “Shocking the Conscience,” “Paranoia and Pandemonium” and “Scare-a-Thon.” This verbiage makes Rucker and Leonnig’s book sound like one more enraged polemic. It isn’t. They’re meticulous journalists, and this taut and terrifying book is among the most closely observed accounts of Donald J. Trump’s shambolic tenure in office to date.

Rucker is The Washington Post’s White House bureau chief; Leonnig is a national investigative reporter for the newspaper. Both have won Pulitzer Prizes. Their newspaper’s ominous, love-it-or-hate-it motto is “Democracy Dies in Darkness.” “A Very Stable Genius” flicks the lights on from its first pages.

Rucker and Leonnig have composed their book, they write, out of a desire to step out of the churning news cycle and “assess the reverberations” of Trump’s presidency. The result is a chronological account of the past three years in Washington, based on interviews with more than 200 sources.