I show it on the picture : the villager sells an enchanted book for 67 emeralds. Sadly, I can only stack 64 of those 😞.
This book is "Efficiency 5".
I think this villager spawned in 1.7.9, and the offer appeared in 1.7.10 (not interesting if you generate offers before they appear ^^).
Duplicate of MC-5506. This should be fixed in the snapshots, and thus the next major release (1.8) of Minecraft.