Kage Baker 
Mammoth Books presents The Books [EPUB ebook] 

In a time beyond the apocalypse, when the remnants of society are trying to restore life to the way it once was, three young circus children go exploring in the town where the circus is camped. As they wander the empty streets they stumble upon a building they will never forget, in which floor after floor is crammed with an abundance of books. This library is heaven for these child survivors of the apocalypse, but they may not be the only ones who feel this way.