Any books featuring the little people with wings of fantasy.
Basically, Tinker Bell or FernGully-styled fairies (or pixies, sprites, or whatever in-universe name they go by).

If you add to the list, any type of book (or age demographic) is fine, but please...

Only add books where they are RELEVANT to the story. In other words, even if the world/universe of a book has fairies in it, only add it to the list if they have an importance to the story (fairies are main/important side characters or they are significant to the plot).