The Cuban missile crisis terrified him and taught him to pay attention to the world. “If politics could force its way into my life in such a vicious and chilling manner, I felt, then I had better find out a bit more about it,” he writes. He became, in Mr. Fenton’s words, “the second most famous person in Oxford” (the first was a student playwright named Mike Rosen) thanks to his fearsome debating skills and his willingness to attend every left-wing demonstration within 500 miles.

Once Mr. Hitchens leaves Oxford, “Hitch-22” is off to the races, detailing his early years as a literary journalist in London, his budding friendships with Mr. Amis and Mr. Fenton and Clive James (among many others), and his Zelig-like ability to be in international capitals when trouble was brewing. “One of the juiciest pleasures of life is to be able to salute and embrace, as elected leaders and honored representatives, people whom you first met when they were on the run or in exile” or prison, he writes.

In the early 1980s  not long after he called Margaret Thatcher “sexy” in print  Mr. Hitchens moved to America. His drift away from the left began in 1989, after the fatwa against Mr. Rushdie. Mr. Hitchens felt that many on the left acted cowardly, blaming Mr. Rushdie for the response to his fourth novel, “The Satanic Verses,” and rationalizing the reaction of Islamic extremists.

This drift continued after 9/11. “When you have seen the Pentagon still smoldering across the river, from the roof of your own apartment building, you are liable to undergo an abrupt shift of perspective that qualifies any nostalgia for Norman Mailer’s ‘Armies of the Night’ or Allen Ginsberg’s quixotic attempt to levitate the building,” he writes.

He supported the invasion of Iraq, in large part, because of his sense of the wickedness of Saddam Hussein’s regime. Before long in this book he is traveling with Paul D. Wolfowitz, a neoconservative in the Bush administration and one of that war’s architects, and referring to “my new friend Michael Chertoff,” then President Bush’s secretary of homeland security.

“An autobiography is only to be trusted when it reveals something disgraceful,” George Orwell, one of Mr. Hitchens’s literary touchstones, wrote. “A man who gives a good account of himself is probably lying, since any life when viewed from the inside is simply a series of defeats.” Mr. Hitchens passes this test, if only by a nose. “Hitch-22” has its share of words like “embarrassing” and “shame” and “misgiving.” He is bitter about the way the Iraq war was actually conducted. And he ruefully admits he has been a less than stellar father to his own children.