Walter Moers created a fascinating universe and stayed true to it all the way through. I'm not sure the plot is so spectacular on its own, but the story was made so by all the details and all the descriptions that he included. It took me awhile to get used to his way of writing, so I wasn't hooked from the very first page, but the further into it I got, the more quirky it became, and I just had to know what happened next.
The City of Dreaming Books uses the book media as a way of telling the story, and I'm always totally charmed by books that dare do that - e.g. write things with smaller font when people are whispering etc. So far I've only seen Walter Moers and Jasper Fforde do this efficiently.
Absolutely brilliant book. I laughed out loud more often than at practically any other book - not counting Douglas Adams obviously, but then he's in a category of his own, and honestly Walter Moers' humour often reminded me of DA.