Mowsh/Minecraft-Enchantment-Calculator — pull request #5 by grgarside (2014-01-02 20:53:36+00:00)
Title: Books can get more than one enchant

It is possible for books to have more than one enchant.

> As of Snapshot 13w39a, enchanting books can commonly yield up to 5 dissimilar enchantments.

Source: http://minecraft.gamepedia.com/Enchanted_book#Enchanting