Re: What is it??
Here's a million-dollar question: What separates the Stephen Kings, John Grishams and Danielle Steeles et al from the rest of the pack? How is it that they can repeatedly write books that command such huge readerships, earning them millions and millions and millions of dollars? What are they doing differently? Does it come down to using genre as a starting point to attract the widest audience possible? Plotting? Creating a certain kind of protagonist?
Yes, yes, and yes.
Genre: books that show up on the bestseller lists tend to certain genres more than others. Technothriller is more popular than SF--more accessible. Fantasy is a niche audience. Romance sells a lot, but not in hardcover. Thrillers of various kinds seem to sell a lot: John Grisham writes legal thrillers, Dean Koontz and Stephen King write horror (or horror-ish) thrillers. The latest NYT hardcover fiction top ten has:
Da Vinci Code (thriller).
State of Fear by Michael Chrichton (thriller).
The Five People You Meet in Heaven (inspirational?)
Life Expectancy by Dean Koontz (thriller).
Night Fall by Nelson DeMille (thriller).
Black Wind by Clive Cussler and Dirk Cussler (thriller). A Salty Piece of Land (by Jimmy Buffett--that probably does more than genre to explain its place on the list)
London Bridges by James Patterson (thriller).
By Order of the President (thriller).
Hot Target by Suzanne Brockman (romance/thriller?)
Lest you think literary novels are completely out of the running, #11 is the new Tom Wolfe. But I think that's a representative sample, no?
Genre and plotting are closely linked, and I think what it comes down to for these bestsellers is what I shorthand as 'narrative force.' Whatever it is that keeps you turning pages.
--A particular style of writing that lets you read the words quickly, get their meaning, and not get bogged down in the beauty of the prose. But there's also an authority in the style: you instantly hear from the author, "I know what I'm doing." It's confident.
--Lots of events happening in short order. Exciting events! Terrorists! Things blowing up! Dinosaurs! Use of cliffhangers to keep us turning pages.
--Complicated plotting that focuses a lot on big events (a couple of those books are terrorism-focused, for example), and not so much on human relationships or intra-personal conflict.
--Characters that are usually very, very competent, characters you wish you were. But they're up against forces as big as they are: victory isn't guaranteed or easy.
I'm saying this not to demean people who write bestsellers, nor to praise them. It's one way of writing; it's a way a lot of people like. Narrative force is incredibly important in all kinds of genre writing--I think all of the above are characteristics of the novels I like to read, but not in ways that are as extreme. I don't think it's the only kind of writing there's room for in the world. I, for one, think I'm more likely to write a good novel by writing the one I'm writing now than one about an eco-terrorist and cloned dinosaurs in Hollywood, but that's me.
If you really want to write a best-seller, read those ten, analyze the heck out of them, pull apart what makes them tick in more detail than I've just done...and see if you still want to write one.