Spyder is a punk kid tattoo artist. Naturally he has a lot of ink himself, and it turns out that one of his cool-looking meaningless rune tattoos has a meaning after all, and it's "Hey you, mosquito-headed demon, come here and eat me." A blind girl with a sword comes out of an alley and kicks the demon's ass. After that life is more complicated.
Kadrey is following Gaiman -- showing us San Francisco Below, the crazy whirl of magical creatures that most of humanity is (pun surely intended) blind to. (What did Mieville call it? Sans Francisco, I think.) Honestly Kadrey is pretty damn good at it. And where Sandman Slim started out as a Hell-tempered killer and got Sue-er from there, Spyder is a hapless kid thrown into Hell. It works better this way. He's vulnerable, and when he runs a familiar-sounding smart-mouth, it comes off as the defense you'd expect of a kid scraping by in San Francisco.
As with the Slim books, there are Tom Waits references (though more with the Orson Welles). As with the Slim books, the fantastic tapestry is weakest where Kadrey leans on traditional Hell imagery and tropes, strongest where he just makes it up. (Though the quick tour of Dante-esque precincts struck an agreeable balance.) Unlike the Slim books, there's just this one, which I'm fine with.