He is best known for his work as a columnist for Time magazine and his novel Primary Colors, an anonymously written roman à clef portraying Bill Clinton's 1992 presidential campaign.

He has also written articles and book reviews for The New Republic, The New York Times, The Washington Post, Life, and Rolling Stone.

It appears in Time's upfront Notebook section and has been criticized for its reporting about then–minority leader Nancy Pelosi and the Democratic opposition to warrantless wiretapping.

In November 2007, Salon columnist Glenn Greenwald wrote about what he alleged were factual errors in a Klein story about the Foreign Intelligence Surveillance Act (FISA).

Greenwald noted that the text of the legislation does not require court review of individual targets, and that Time's response disregards this fact.

"[13] Greenwald has reported that Senator Russ Feingold has been informed by Time that his letter rebutting Klein will be published in a forthcoming issue.

[14][15] In October 2012 Klein was criticized by Glenn Greenwald for revealing on MSNBC's Morning Joe program his advocacy of U.S. drone strikes.

Klein dismissed child deaths caused by drones in the countries where they are operating, stating that the bottom line, in the end, was to ask "whose 4-year-olds get killed?

"[16] In a June 2013 cover story for Time magazine, Klein reported on Oklahoma tornado relief, but came under fire for implying secular humanists did not help deliver aid.

[17] Klein later clarified he only meant to refer to "organized" secular humanist groups,[18] a claim that was also contested and called inaccurate.

He said radical-middle activism was fueling "what is becoming a significant intellectual movement, nothing less than an attempt to replace the traditional notions of liberalism and conservatism.

In the book, he wrote: "The conventions of journalism prevent me from fitting too neatly into one political niche (although as a columnist for the New Yorker and Newsweek my predilections are obvious).

[29]American foreign policy scholar Max Boot and the Anti-Defamation League national director, Abraham Foxman, were among the critics of Klein's views.

We were deeply troubled by your outrageous assertion on Time Magazine's "Swampland" blog that Jewish neoconservatives "plumped" for the war in Iraq and are now doing the same for "an even more foolish assault on Iran" to make the world "safe for Israel.

"In an interview published in The Atlantic magazine discussing the controversy, Klein stated When Jennifer Rubin or Abe Foxman calls me antisemitic, they're wrong.

[1] As of 2009[update], Klein lives in New Rochelle, New York with his second wife, swimwear designer Victoria Kaunitz, with whom he has two children, daughter Sophie and son Teddy.