Overall, I did enjoy Neverwhere, though not unreservedly. Similarly to To Be Taught, If Fortunate, I'd heard very good things about Neil Gaiman as a writer, just had never read one of his books before.
Neverwhere, I believe, is a novel based upon the scripts for a television series (though I have never seen it), rather like one of my favourite books: The Hitchiker's Guide to the Galaxy. This is not were the similarities end, as Neverwhere feels very much like Hitchiker's in its setting and humour. They both take a very irreverent view of modern society and shape that into a fascinating world.
As a big fan of Douglas Adams, this should have primed me to fall in love with the book straight away, but it never quite 'clicked' for me. I found the humour somewhat forced and, just as I would get immersed in the world, a witty aside would pull me straight back out again and distract from what was otherwise an enjoyable book and very interesting setting. Gaiman's characters are also often a little flat, and frequently commit violent acts (chewing on birds and rodents seems to a popular past time in the book) for no other apparent reason than to shock the reader.
Aside from the humour, the world Neverwhere is set in is fascinating, many of the characters interesting (though not the most gripping), and plot enjoyable. It was a interesting read and one I will almost certainly revisit.