When author and film maven William Goldman had his famous epiphany—"Nobody knows anything"—he was writing about the film business and how moviemakers, clueless to what "works" on screen, took a what-the-hell attitude toward their creations.

As I remember it, Goldman's point was mostly negative—filmmakers were clueless and their cluelessness was the reason so many movies were bad or terrible—but when I think about it now, I realize there might be an upside to this ignorance. Sometimes, the less you know, the more creative you can be. As in: oh, well, since nobody knows anything anyway, we might as well take some chances, try some new things and hope for the best. We all know, after all, that genius—or at least good product—often grows from uncertainty and doubt.

When it comes to books, of course, "nobody knows anything" also applies—although this being publishing, we usually dress the idea up in prettier clothes. "What I love about this business is the serendipity of it," one longtime agent recently ventured. Others call it "magic" or "gut instinct." In the end, the descriptions all translate the same way: what makes a book work is, ultimately, unknowable and most likely unforceable. You probably just have to throw a lot of things at the wall to see what sticks.

And as in filmmaking, this philosophy can work to creative advantage, and there certainly are many editors, authors and houses who go out on artistic limbs on a regular basis, and try not to repeat themselves. All too often, though, publishers are more entrenched and nervous than enlightened and free. They find something that "works" and they scramble around to try to repeat it. Get me the next XYZ, they say. Or, more often, get writer XYZ to perform his magic trick again.

How else to explain Simon & Schuster paying a reported $2 million for Everyone Worth Knowing, Lauren Weisberger's follow-up to the surprising (to me) bestseller, The Devil Wears Prada or Broadway ponying up the same-ish amount for a "sequel" to He's Just Not That Into You? Both of those original books were blockbusters, way out-earning even the most optimistic author/agent/publisher dreams (although it's interesting that their original publishers, Doubleday and Simon & Schuster, respectively—bowed out when the bidding went stratospheric for the second books). To judge by their first weeks barely clinging to bestseller lists, neither sequel will end up with the life, or legs, of the original.

I haven't read them, but I'd bet that neither of these follow-ups is particularly worse than the one that spawned it. So why haven't they worked? Maybe because the rotely repetitive publishing philosophy behind them didn't take into account the value and luck of tapping into the perfect moment in the zeitgeist (for this year's version, see: Freakonomics). For books that are more parlor trick than creative turn, timing is all—and like most parlor tricks, they get pretty boring the second time around.

And you'd think by now, publishers would know better—do I have to say Nanny Diaries?—but never mind. "Nobody knows anything," remember?

Nobody, that is, except for the customers who buy—or don't buy—second books.