This is brilliant. The concept is brilliant but you also nailed the atmosphere of the library.
I know this sounds strange but in the game I really felt like jumping and especially sitting (or simply crouching). Like... jumping to get a book that's on one of the higher shelves and then just sitting down and look around while seated. Sitting down with the book would also be +++ but even without that, I feel like sitting down would have been very satisfactory.
But yeah, again this is absolutely brilliant. Having different kinds of randomness in different books was an excellent decision. Your game is a good experience. :)