Weaveworld

This is a novel by Clive Barker.

My first opinion of it, after having read about 100 pages, was that it was Neverwhere, only worse (because obviously no one can match Neil Gaiman's style.) And, I stand by that judgment as it regards the first 100 pages. However, the story manages to diverge in the following 500 or so pages and really becomes a world that the reader can get lost in.

So, if you like the plot of Neverwhere, I recommend Weaveworld as a good read.