Photoshop Retouching Cookbook for Digital Photographers: 113 Easy-to-follow Recipes to Adjust and Correct Your Photos by Barry Huggins
This book runs the full gamut from correcting basic exposure, through fixing problems with lighting and focus, before going into detail on portrait work, landscapes, effects, and restoration. While packed with information that will help any Photoshop user raise their game, the strength of the book is the way it concentrates not on effects for their own sake, but on the hard-working image-editing skills that photographers really need.