"Oh, he is marvellous, he knows his household pests, all right, it's a wonderful book..."
-- Molly Weasley (CS3)
Gilderoy Lockhart’s Guide to Household Pests is a guide to various common magical pests.
It seems ironic, given Lockhart's true nature, that this book is so useful. All of his other works that we know about are written in a memoir style (easy to fake by just writing out stories other people have told him), whereas this book actually requires knowledge and expertise in the area. Was someone else perhaps working on researching and writing a pest guide, and mysteriously forgot about it? --RP