This is the first novel by Neil Gaiman that I have read. I thought the idea of the story - that of an alternate London underneath - was very original and interesting. I found the book really fun and interesting up until the bit where they started wandering around. It just didn't seem that after that the book really went anywhere. I had a hard time picturing what was going on, and some of the characters seemed poorly developed.
On the other hand, the book had a healthy dose of humor, which is always appreciated. I liked that it was different from the typical fantasy setting (I could not be called a huge fantasy fan, to be honest...) I will read more novels by this author, and I would recommend this one with a few reservations. It is a reasonably quick and fun read.