I think that all of us who write struggle with one big question: what do readers want? And it's a really difficult one. No-one knew that readers wanted Harry Potter until Bloomsbury finally picked it up, and no-one could have predicted that Lynne Truss's Eats, Shoots and Leaves could have become a runaway bestseller. Truss's book had a small initial print run, but it just went on selling. A wonderful and deserving book, but it was genre-less, and no-one could have expected so many readers to want to read a book about punctuation. So her follow-up about modern manners - Talk to the Hand - should have sold well too, shouldn't it? But it wasn't nearly so successful. Then there was Stephen Hawkin's A Brief History of Time; another bestseller (although apparently most people never managed to get through it; it was far too complicated. I knew better than to try). And the lovely No 1 Ladies' Detective Agency series; hardly a conventional read, but very successful indeed.
So maybe we don't know what readers want quite simply because they don't know, either; that is, until they find it. And then they realise that that's exactly what they wanted all along. As a reader, I can understand that. But as a writer, it's of no help at all!