OK, at times it got a little gimmicky and repetitive. (There's only so many times you want to hear a narrator imploring the reader to "burn this book... now!") However, as it went on, it grew on me.
The narrator, a very minor demon from a horribly abusive family, keeps sucking you in to sympathise with him - and them reminding you that no, he really is kind of evil, when you get right down to it... but no, he's just a poor little put-upon demon!
It starts as a bildungsroman, as the young demon, Jakabok Botch, goes out into the world, has an obsessive affair with an older demon... this part of the book is good enough. But the end, with Johannes Gutenberg as an essential character, and, of course, the Great Secret of the conflict between Heaven and Hell, is excellent.
Clive Barker is always an entertaining and clever writer, and in the end, this book does not disappoint.
Also - the book itself, as a physical object, is lovely. I love it when publishers bother to put money into making a book look nice. The faux-aged pages and old-fashioned font really work.