We know them as major 20th century writers, but to the FBI, Susan Sontag was a “subversive,” James Baldwin a “pervert” and Hannah Arendt “a small, rotund, stoop shouldered woman with a crew-like haircut, masculine voice and a marvelous mind.”

Under J. Edgar Hoover, who ran the bureau from 1924 until his death in 1972, the feds amassed files on countless Americans, some of whom were well-known novelists, historians, and journalists. Most of this information remains hidden from public view. But in Writers Under Surveillance: The FBI Files, we get a look at some of the facts and hearsay that was gathered on 16 prominent authors. It’s a fascinating and at times hilarious book. You could argue that it’s an important one, too.

JPat Brown, who edited the book with B.C.D. Lipton and Michael Morisy, describes the files as “stolen history.” He and his colleagues at MuckRock— a nonprofit organization that helps citizens and reporters access government documents—got hold of the files through copious Freedom of Information Act requests. Winnowed down to 20 or 30 pages per writer, the files are carefully organized and easy to navigate; each is preceded by an introduction placing the material in context.

“This is actual historical material about what was being done by public servants in the public’s name,” Brown said in a recent interview, “and I think that that material should be part of the public record. It should be something that we all know and can learn from and make decisions based on.”

The book makes clear that during the Cold War, there were lots of things a writer could do to arouse the bureau’s interest. Those who made disparaging comments about Hoover himself, or were deemed to be insufficiently loyal to the US, were apt to end up in an FBI file. Ditto for drug-users, civil rights and antiwar activists and anyone who visited North Vietnam or Havana. Which is why Baldwin, Sontag, Arendt, Truman Capote, Allen Ginsberg, Norman Mailer, Hunter S. Thompson, W.E.B. Dubois and others show up in these pages.

Ginsberg, for one, went to Cuba in the '60s. He also liked his drugs, so naturally, the FBI opened a dossier on him. His file includes comical details that make you wonder what Hoover’s agents thought they were accomplishing. One memo notes that “the ‘New York Times’ issue of March 15, 1960, contained an article reflecting that in Prague, Czechoslovakia, there is a café called Viola, which is a Greenwich Village type. The article stated that the works of Ginsberg were read there to jazz accompaniment.”

The bureau decided that if someone was going to lead an insurrection, it wouldn’t be Ginsberg: “His activities, while bizarre, have not indicated any direction or being inimical to the interests of the US.” The FBI appears to have drawn similar conclusions about Arendt, the German-born author of The Origins of Totalitarianism, and Sontag, who went to North Vietnam and subsequently published Trip to Hanoi.

W.E.B. Du Bois, on the other hand, was indicted by the Justice Department in 1951—a decade after the FBI opened its file on the African-American author. The charges—that he failed to properly apprise authorities about the anti-war activism he took part in abroad—were eventually dropped, but the FBI kept an eye on him until the ’60s. “The final remaining entries of his file see Du Bois leaving for Ghana, where he would eventually die, after the US rejected his petition to renew his passport,” the book’s editors note, “forcing him to become a citizen of the newly-formed African country.”

Ray Bradbury’s file captures the anti-Soviet paranoia of the Eisenhower era. According to a 1959 memo about the FBI’s interview of Martin Berkeley, a screenwriter and “self-admitted former member” of the Communist Party, the author of Fahrenheit 451 was potentially part of a Red cabal: “Berkeley stated it has been his observation that some of the writers suspected of having Communist backgrounds have been writing in the field of science fiction and it appears that science fiction may be a lucrative field for the introduction of Communist ideologies.” The FBI didn’t pursue Berkeley’s claims.

The files have a way of posthumously puncturing big egos. Norman Mailer may have believed he was his era’s most important voice, but the bureau didn’t agree. His file features skepticism about the research he did for his biography of Marilyn Monroe and criticism of the prose in Miami and the Siege of Chicago, his report on the 1968 Republican and Democratic conventions. “Mailer vacillates greatly in his thinking,” reads one memo, “making this book difficult to read and impossible at times to comprehend.”

The file on Capote, meanwhile, contains a memo about a phone call from a Random House editor to the FBI. The editor, whose name has been redacted, wanted the bureau’s help as Capote began scheduling interviews with police and others for In Cold Blood. When Capote went to the Midwest to begin reporting, the memo explains, he “did not take any credentials, as he felt his many articles in ‘The New Yorker; had given him a national stand(ing) as a writer and he is quite crushed to think that the [redacted] of Garden City, Kansas, has never heard of him.”

FBI agents aren’t the only ones whose writing appears in the files. Letters from citizens are alternately naïve, menacing and funny.

In 1970, a Louisville resident wrote in to report that Hunter S. Thompson—“the bad boy of our neighborhood”—might’ve been arrested in his city around 1954. “I would sign my name but am afraid I might be sued,” he explained. “I am interested in good government.”

In addition to Hoover’s contention that Baldwin, who was gay, was “a well known pervert,” the file on The Fire Next Time author contains a letter about the writer’s appearance on David Frost’s talk show. “With much gesturing and eye-rolling,” an unnamed citizen reported, Baldwin criticized President Richard Nixon and said the federal government targeted young black men. The letter-writer wondered if the TV station should be allowed to keep its license. Hoover was moved to respond. “I certainly understand the concern which prompted you to write,” he replied, promising to forward their correspondence to the Federal Communications Commission.

In Ken Kesey’s file, there’s a request from a high school student who was researching the life and work of the One Flew Over the Cuckoo’s Nest author. The student wanted details on Kesey’s criminal record and childhood: “Please rush this information if possible. Paper is due in two weeks.”

“These stories, even the funny ones, hammer in how omnipresent government is in our lives in a real and meaningful way,” said MuckRock’s Brown. Indeed, as Trevor Timm, executive director of the Freedom of the Press Foundation, writes in the book’s afterword, “The FBI now has tools at its disposal that Hoover could scarcely dream of in the 1950s and 60s.” In the 21st century, the bureau’s “informant machine has lasered in on America’s Muslim community,” as well as “Black Lives Matter organizers, environmental activists, and even journalists.”

The book, published by MIT Press, is the first in a planned series, and according to Brown, there’s a surplus of files from which to choose. “Under the Freedom of Information Act, once you die you no longer have the right to privacy,” he said. “And because they’re never going to stop making dead celebrities, there’s going to be an endless supply of people we can request.”