As you want to trade with a healed zombie villager or a villager with "hero of the village" effect applied, you cant buy enchanted books from them. 

What I expected to happen was...:
Trade books for enchanted books with villagers

What actually happened was...:
As I click to tarde with the villager, the book doesn't show in the box

Steps to Reproduce:
1. Heal a zombie villager
2. Put a lectern near him
3. Search for the book that interest you the most

4. You can't trade