A few notorious books published as nonfiction have brought to light a little-known fact: Publishers don’t fact-check their books. They take their authors’ words for the truth. The poster child of the unfortunate result was Greg Mortenson’s Three Cups of Tea. Mortenson and his coauthor allegedly stretched and fabricated the truth about building girls’ schools in Pakistan.

Beyond the ethics of nonfiction writing, Mortensen’s transgression points to a lesson for authors doing research: Don’t use any published document or book as if it were a primary source unless you double-check the facts.

A good practice is to email facts, quotes, and/or manuscript passages to all key sources in your book to check. No matter how meticulous you thought you were in writing, you’re sure to be surprised—and pleased—to get the facts right.

In my book, Merchants of Virtue, over half of the 47 people who responded to my fact-checking requested submitted corrections. Some of the “corrections” struck me as preferences. Others related to minor facts—confirming a mug was plastic and not ceramic. But some affected how I had construed critical conversations. In one case, I had put quoted words in the mouth of the wrong person.

So what’s your responsibility as a book author? This is a personal decision, but one you should make it in advance of writing your book. What and who will you trust? What facts will you check?

If you don’t want to make a published mistake, go back to all interview sources and double-check quotes, numbers, and the general veracity of what you’ve written.  Find a third party to corroborate all secondary sources. Even honest people often exaggerate or gloss over inconvenient facts during casual interviews. Double-check quotes even if you have recorded the interviews.

Gay Talese, one of the masters of nonfiction narrative, once said he never records a first interview. Why? Because people so often shoot from the hip, saying things they don’t really mean, So what’s the use of a recording? He’ll go back a day or two later and, having taken notes on the trenchant quotes or anecdotes, ask his sources if they really meant what they said. A verbatim transcription won’t help with getting the facts right if your source has embroidered the truth.

When it comes to using secondary sources, remember that even reputable magazines and newspapers err or omit relevant facts (even publications like the New York Times and Fortune). It’s not a matter of dishonesty or carelessness. It’s that you can easily misinterpret what was said—and that reporting free of errors or misimpressions is so hard. If a publication cites a case, a survey, or an expert’s testimony, get the original.

In The One-Minute Meditator, a book I co-authored with David Nichol MD, we started one chapter with a quote we believed came from Henry David Thoreau: “The soul grows by subtraction, not addition.” A few months after publication, the curator at the Thoreau Institute at Walden Woods emailed me. He wanted to verify the origin of the quote, because he could not find it in Thoreau’s writings. That’s when I really did my homework—and had to admit I hadn’t corroborated it. The staffer was able to verify the quote really came from Meister Eckhart, the 13th-century German mystic.

The lesson is that when you’re done with your manuscript, check everything. Bear in mind that during editing, magazines and newspapers you rely on often “tidy up” the facts in a way that retains veracity but leaves out caveats. And that when the “facts” often get misinterpreted, and once they are published, they take on a life of their own: That’s when you realize that their only source is endless repetition in cyberspace.

If you build a book on other people’s research and reporting, you’re likely to pay dearly later under cross-examination by astute readers.  Better to remain a skeptic. Budget time for fact checking. You’ll feel good about getting everything right—and you’ll avoid embarrassment.

[Revised January 2020. Originally published April 16, 2011]