I was randomly playing on a new world in the 15w34d Snapshot when I came across a dungeon. When I looked in the chests, there was the regular loot and an enchanted book inside. When I went to check the enchant on it, I saw it had none. When I tried to Enchant any type of armor or tools using the enchanted book it was not compatible with anything. After, I created a superflat desert world to check if it was the same in a Desert temple, and when I located one with an enchanted book inside the loot chest, unfortunately it was. The Enchanted book has the same appearance as usual but does not feature any enchantment.