I thoroughly enjoyed this book. I think it should have been in the young adult section of the library, but that's okay.
I love the world that Moers created. An entire city devoted exclusively to books! Even the food was somehow related to books either by name or shape. A city of bookstores, just think of it! (I'd be broke in no time).
The underworld was even more rich. I adored the booklings though I admit, it took me far longer than it should have to realize that their names were jumbled versions of real author names. I suspected, but I'd always been terrible at those things so it wasn't until a passage was quoted and I unscrambled the name that I confirmed my suspicion. (And I never did figure out who the adventurer was supposed to be. Anyone else know?)
It brings up an interesting question because the book was translated from German so I wonder if the translator substituted authors and passages that would be more familiar to an English/American audience. (There was one example of British spelling so I'm not sure which audience it was translated for). There's also a section that deals with very old rarely used words and those words were also very old English words so again, I'm not sure how that was reinterpreted. Did he randomly pick old words or try to find old words similar to the no longer used German words?
There was also an interesting tension between reading and owning books. For most of the people in the book city it seemed owning was more important but for the protagonist what the books actually said was at least as important. I'm not sure it was more important, at least in the beginning. It was hard to tell if the books on the Golden List were there simply because they were rare or because they were made of rare materials and if the quality of the literature played any part in determining what was on the list.
It really was a wonderful, fantastic (in the sense of fantasy) adventure.