This book is a bit like a movie where the cinematographer and the set designers locked the director in the basement and took over the set. Its very atmospheric, its filled with all sorts of wonderfully intricate and particular detail, and yet it rambles all over the place without ever gelling into anything coherent and parts of it go on much too long and don't make enough sense.
The conceit is that its a bunch of loosely associated parts - stories, articles, reports, footnotes, letters, perhaps from a very strange city called Ambergris, or perhaps from the cell of a madman. I am actually really attracted to the concept and I wanted it to work, but it wore thin for me pretty quickly and I found myself just irritated.
That said, it is both atmospheric and ornately detailed and that can be fun for a little while. Sort of like one of those eighteenth century shell grottos - at first you are a bit fascinated but after awhile you just want to go outside and get some fresh air.