Editor’s Note: Sara Nelson is the editor in chief of Publisher’s Weekly, the industry’s leading news source, covering every aspect of creating, producing, marketing and selling the written word in book, audio, video and electronic formats. 

How do you make a bestseller? That’s one of the most important and oft-asked questions in BookLand.

We don’t know the answer, so, of course, we’ve established some rules:

Rule No. 1: Never publish an author posthumously. Publicity tours, whether satellite or in person, are key, and dead people don’t travel well. Next, forget books in translation. Only about three percent of our total annual output began as non-English language, so it doesn’t take a math genius to figure what percentage of those books end up on the bestseller lists. And while you’re at it, don’t count on the sensitive, first great American novel, especially if it’s a doorstop; Gone With the Wind was a long time ago.

So here’s the thing: Often, the rules don’t hold.

Take, for example, our hardcover nonfiction bestseller list: In the No. 1 spot is The Last Lecture by the late Randy Pausch (and Jeffrey Zaslow). While Pausch was alive when the book pubbed, it really jumped up the charts when he died — and the book was all about dying, anyway. Check: rule No. 1 broken. Ditto for the 14th slot on our hardcover fiction list – The Girl with the Dragon Tattoo author Stieg Larsson died soon after completing and selling three manuscripts, which are already hugely successful in Europe. (The novel is also translated from the Swedish — take that, rule No. 2 — and is arguably the most successful literary export from Sweden since Astrid Lindgren’s Pippi Longstocking franchise.) As for rule No. 3, The Story of Edgar Sawtelle, a long, dense Hamlet-on-the-plains novel that practically screamed midlist to everybody except Ecco’s Lee Boudreaux, currently sits at No. 3 and, partly thanks to Oprah, is said to have shipped 1.4 million copies.

And that’s in hardcover.

Another rule that doesn’t always hold: “All ink is good ink,” and its corollary, “controversy sells.” The Jewel of Medina the novel about Islam that was dropped by Random House and later picked up by Beaufort, sold a respectable but unspectacular 3,000 copies in its first ten days, according to Nielsen BookScan. On the other hand, some things you can predict: Nicholas Sparks will land high on any fiction list, ditto any offering from John le Carré or Candace Bushnell. (The latter suggests yet another rule, inevitably, eventually to be broken: Get famous for a TV show — even one that didn’t much resemble the collection from which it took its name — and you’re a star author.) And in an election year, you can bet that at least some political books will hit. Which ones, you ask? Ah, there’s the question.

This unknowability can be frustrating, of course, and heads are being scratched all over town about, say, the success of the originally self-published faith novel The Shack (the Windblown Media edition has been No. 1 on our trade paperback list for 20 of its 29 weeks) and plenty of other titles. Still, most book people, if they’re honest, will tell you that it’s that unknowability that gets them out of bed in the morning and makes them want, even in hard times, to keep publishing.

“We keep doing this because this is what we do,” one veteran publisher told me last week in Frankfurt. Put it another way: Discovering a book that works is like finding true love.

You take your risks, you make mistakes, and you start with your heart.

And, sooner or later, you break the rules.