A few years back, I was at Worldcon, and I listened to a panel with Walter Mosley. He told a story about being in a bookstore and seeing one of his science fiction books shelved in mystery. He took it to the information desk and explained that it was in the wrong section. The infodesk critter said “On no, that’s Walter Mosely. He writes mystery.” Mosely said “I’m Walter Mosely,” and he said he could see the guy thinking and you write mystery.
Authors names are brands for their writing, whether we like that or not. And I have had a lot of people tell me that they aren’t like that, that they’d follow a writer they like to any subject matter.
The evidence is that they’re in the minority. If that were true, more people would have read Stephen Donaldson’s Gap series. John Grisham’s baseball novel would have found its audience. Booksellers wouldn’t have said that Walter Jon Williams – one of the best writers in the field – is hard to sell because he’s written so many different things that no one knows what a “Walter Jon Williams” book is. Even George R.R. Martin. If anyone has a name to conjure with, you’d think it was George. But I co- wrote a novel – Hunter’s Run – with him, and the Song of Ice and Fire fans didn’t pick it up. I think the way you meet peoples expectations is tell them what they’re going to get with the name of the author. Richard Stark wrote straight-ahead crime thrillers, Donald Westlake wrote humorous ones. Daniel Abraham writes epic fantasy, James. S. A. Corey writes space opera, MLN Hanover writes urban fantasy. Walter Mosely writes mystery.
Now there are places you can play where that doesn’t happen. YA fiction, for instance, has a different dynamic. And as far as I can tell, no rules apply to Neil Gaiman.