What if God was one of us - just a slob like one of us, just a stranger on the bus trying to make his way home? --Joan Osborne
What if, when the first people started immigrating to America, they brought their gods with them, literally? What if, because they believed/paid homage/sacrificed/etc. to the otherworldly beings of their homeland, those beings actually traveled over land and sea to take up residence in the New World with their believers? That's pretty much the basic idea behind Gaiman's novel.
We meet our protagonist, known to us only as Shadow, just as he's about to get out of prison after a 3-year stint. He's made some mistakes, but he's not a bad guy. He's got a wife and new job waiting for him at home, and he's about to put his life back together when the proverbial rug is pulled out from under him, sending him tumbling into a world he never knew existed. Suddenly he's in the middle of a war between the old gods (who are losing their power as their believers have died out, leaving them forgotten and abandoned by the rest of humankind) and the new gods of commerce, technology, and entertainment.
The novel is almost as much a mythology lesson as an entertaining narrative, and a long one at that (over 600 pages). There are several little side stories along the way, offering explanations of how the various gods were brought to their new - and eventually unsuitable - home. It's a fun read, though, with a couple of twists at the end; you think you've got it figured out, and then Gaiman tosses something else at you in a "Haha! Not so fast!" sort of way. The overall conclusion wasn't completely satisfying to me, but I think the book was so long that it would be hard to wrap it all up in a better way. In sum, an amusing read, and one I'll recommend. A-/B+