I'm not an adventure reader. I won't buy a book unless I've read more than a few chapters of it. I buy books mostly that I have read, liked and want to read again. I hate wasting money on a pig in a poke which turns out to be a dud. I know the authors think you'll just rush out to buy what they write. I don't and a lot of others don't.
When I DO like something like the Jak Barley series, I immediately buy the next. There are authors I buy the new book from site unseen. I can count them on one hand. I have bought books I haven't seen but they were out of print classics of certain genres you can't even find in a bookstore. And considering the publishing standards at the time they were printed, I wasn't disappointed in them.
Neil Gaiman is an incredibly talented writer who can write and maintains a certain standard in his writing that makes him a professional. His Dr Who tv episode, the Doctor's Wife, was fantastic and was a story any married couple could related to even if they had never watched Dr Who before. He tends to transcend and reach into human existence. Instead of telling stories, he tells a story. He tells you personal things about his characters which touches something in you so you know those people and they are real.
He really doesn't have to worry about being a one trick pony who can only write one thing and has to fear for the next buck. He writes out of love and he would do it, I think, even if he were pushing shopping carts around a Walmart parking lot for a living. And I can't see him complaining about pirates even then. I rather think he would be more worried if the story got across.
Some do what they love and some don't. It shows. And it also shows in what they worry about. One trick pony's worry about pirates. Writers don't.