It says punk on the cover. But I'm blowed if I can see how Gaiman is punky. Do his characters gob at one another? No; they are perfectly behaved and their hearts are pure. OK, so the villains are pretty gross. But so is Gollum. Does that make Tolkien a punk? I don't think so.
All good fantasy is rooted in Victorian values and a Victorian aesthetic. This is because the Victorian century is a bridge between the old world and the new. To my left the blessed damozel, to my right the 4.10 from Euston. The gothic coexists with the mechanical. It's no accident that Dr Who, in all his incarnations, is a Victorian gent or that the Hogwarts express is powered by steam.
Gaiman is in a long line of writers who have explored and expanded the myth of London. On his title page he acknowledges his debt to one of the greatest of them- G.K. Chesterton. Behind Chesterton lie Blake and Lamb and Dickens and after him come Woolf and Eliot and Moorcock. London is the ultimate city of fantasy. Paris? New York? No I'm sorry, but no other city has inspired such a wealth of fantastical poetry and fiction.
So back to Neverwhere. Door and Richard have just encountered the Angel Islington in the British Museum and the Marquis of Carabas (the rotter) is conferring with Croup and Vandemar in the cellar of the abandoned hospital among a litter of razor blades and half-eaten kittens. I can't begin to imagine what happens next...