Charlie Nancy is a regular guy, but his father is Anansi, the African trickster spider-god, who is "the spirit of rebellion, able to overturn the social order, create wealth out of thin air, and baffle the devil." When Dad dies, Charlie finds out he has a brother he never knew about, who is the spirit and image of the old man. This brother -- Spider -- thinks Charlie's life is too boring and predictable and he promises to liven it up. A promise he keeps, as within hours Charlie is fired from his job, cuckolded by his girlfriend and wanted by the police. And from there, things get a whole lot worse and a whole lot weirder.
This is a sequel of sorts to Gaiman's "American Gods", and I actually like this one better. "Gods" was epic in scope but in this one we see things mainly through Charlie's eyes and he is easy to relate to. There's more humor here too, and along the way Gaiman makes some great points about why we love to tell ourselves stories, and why it is important that we do so:
"The stories spread, and as people tell them, the stories change the tellers. Because now the folk who never had any thought in their head but how to run from the lions and keep far enough away from rivers that the crocodiles don't get an easy meal, now they're starting to dream about a whole new place to live. The world may be the same, but the wallpaper's changed. Yes? People may still have the same story, the one where they get born and they do stuff and they die, but now the story means something different to what it meant before."