I've read a few of Neil Gaiman's fantasy novels now as well as watching the film Mirrormask, for which he wrote the script. I've enjoyed all of them in that "I just want to keep reading this" way that good genre novels should have.
However, I've started realise that he has a template. All the stories he tells are variations on the one story which goes roughly like this. A well-intentioned but hapless young man is trapped in a rather unsatisfactory life. He works in a dead-end job, is in a relationship with a woman who is wrong for him, and is stumbling down the slope to a sub-optimal life. Then some apparently chance encounter or freak event tips him into a completely bizarre parrallel world, in which he must achieve (or help someone achieve) some great and incredibly dangerous task in order to get back to his old life. In other words, these are quest stories.
My most recent (but Gaiman's first) is Neverwhere, in which Richard Mayhew, mild-mannered London accountant and fiance to the formidable Jessica, finds a young homeless woman bleeding from an injured shoulder. His innate sense of compassion makes him ignore Jessica's protests, take her home and help treat her injury. As a result he is literally tipped out of his life (ordinary people are no longer able to see him and his friends and colleagues have forgotten his existence) into the world of "London Below", a bizarre realm of homeless people, forgotten places, talking rats, mythical creatures and incredibly dangerous assassins. Here he has to help his new friend, the Lady Door, and her odd and slightly suspicious group of companions to find out who had her family killed, and why.
Because it's a quest story you know it will work out OK in the end. Just like it does for Charlie Nancy in Anansi Boys, or for Shadow in American Gods. Yet despite knowing the ending you keep reading. Partly it's his skill as a writer dragging you along, revealing unexpected twists just as you think you might know what's happening. Partly it's that you want to understand the new, mysterious world Gaiman has created, which he shows bit by bit like a conjurer. Partly its because you like his characters, and really want things to turn out right.
There's also the fact that you're trying to work out exactly what "right" is. Richard wants his job back, and his flat, and his fiance. But does he, really? You feel like screaming at him, "No, don't marry Jessica and spend your life as an accountant!" And of course that's the point of a quest. You could go back to where you started, but it will not be the same for you because you have changed. Richard returns to a group of people amongst whom he is a slightly hapless accountant, but in London Beneath he is a warrior, knighted by the Earl of Earl's Court, friend to the rats and birds, companion of the Lady Door. Which calling will he follow?
I think ultimately the power of these stories (and they are tremendously popular) is in their psychology. Gaiman is showing us that beneath the surface of our lives there is so much more than we acknowledge. Not only are there people all around us who we don't notice - homeless, mad, fogotten people who could possibly turn out to be gods or mythical heroes - but there is a whole world of feeling and ambition, danger and possibility, that runs beneath the surface of our ordinary lives. We rarely acknowledge it, we live as if it were not there, but if just once we allowed it to take hold of us we would never be the same again.