I read Neverwhere on Christmas break from college. I hadn't been reading any fantasy or science fiction, really, and was blown away by the idea of an alternate world existing in the London subways. It just felt so wonderfully escapist. I was also shocked by the juxtaposition of humor and horror. It was the first thing of Gaiman's that I read, and it was the book that helped me get past my college pretensions and get back into the SF/F genre I'd loved so much as a kid. So I was pretty excited when I stumbled across this today because I've been hoping for a movie adaptation for 10 years now. (Yes, I've seen the BBC version.)
According to
this site, Neverwhere is heading to the big screen with director David Slade (30 Days of Night and Hard Candy) using Neil's script from 2000 as the basis. I haven't read about this anywhere else, on Gaiman's blog or AICN or anything, but I hope this is true.
I also haven't seen either of the movies Slade has made but what I have seen of 30 Days of Night looks promising, dark, moody, and terrifying. All which would be important with Neverwhere.