retouching books
Photoshop Restoration & Retouching - Kartin Eisman
Skin - Lee Varis
Commercial Photoshop Retouching - Glenn Honiball
Glitterguru on Photoshop - Suzette Troche-Stapp
dharmazenbook - small but good book
Making Faces - Kevin Aucoin - this is not a photoshop book, but a makeup book. As much of retouching is based on makeup, this would be a good read for those interested in digging deeper.