This is one of those young adult novels that straddles the border of fantasy and science fiction. I think some of the ending is supposed to tip it over into definitely SF, but I'm not completely convinced and am much happier if I just think of it as an inhabitant of border provinces.
It's also one of those young adult novels that is explicitly, completely, for people who love books passionately. While the overarching message seems to be that literacy is good and that sharing knowledge is good, it's very much a book for preaching to the choir--I can't imagine someone who isn't already fascinated with books attaching to this one with any enthusiasm. It's not a book for conversions. And the overarching message is very strongly present. There really isn't much book there without message. I also thought the two sides of the story were too carefully balanced for believability.
I liked what North (which is a pseudonym for--well, her agent's page comes right out and says it's a pseudonym for the person who writes SF as Anne Harris, so I don't think I'm spilling any big secret, but if somebody knows otherwise, please stop by and say) did with the idea of the chosen one, though. People who like playing with fantasy tropes in that way might well enjoy what happens with that at the end. In fact, I thought the last third of the book was much stronger than the rest--I preferred Haly's insistence that she was a clerk, not a full libyrarian, to her somewhat formulaic interaction with the libyrinth bullies.
The title word bugged me some. It's clearly Library + Labyrinth, with a hint of Liberation as well, but like most portmanteau words--see Anathem over and over again for other examples--it struck me as not really as clever as its author had hoped, and having the libyrarians of the libyrinth made me feel like I was dealing with a 4-year-old who can't say "librarian" properly--the lie-buh-rarians work at the lie-berry in my head. Meh. Little things.
I am also frustrated that the ad copy seems to be focusing on only one of the plot threads, when I liked the other character better. But my favorite bit with her is a spoiler, so...yah. I have a favorite bit completely not hinted at in the ad copy, is what, down to which character it happens to. I wonder if the people writing the ad copy had the same problem I'm having, where it was a lot easier to articulate little nits to pick without spoilers than to describe the larger things I liked. Hmm.