These are a just a few things that keep me reading, and they are also things I consider when writing fiction. Writers need to look at their work from the reader's perspective, though, so they should absolutely know what readers want.
1. Good writing with all the pretty shiny words in all the right places
2. Memorable characters
3. Strong protagonist
4. Just enough back story. "Never let the history get in the way of a good story." Can't remember who wrote that.
5. I want to finish reading a novel and "know" the main character, confident the writer also knew the main character because often he or she doesn't. I sometimes close a book and think, "She wouldn't have done that." The story and characters need to be believable and consistent.
6. I want the story to hang around in my head after reading it. I want a story I can mull over and think about for a while.