GIMP 2.8 for Photographers: 
Image editing is a crucial element in the photographic workflow. Image editing tools, most notably Photoshop, are usually sophisticated and deep applications, and are fairly expensive. The only open source tool in this market is the GIMP, which has developed into a powerful, multiplatform system running on Linux, Mac OS X, and Microsoft Windows.
GIMP 2.8 for Photographers is a beginner’s guide to the only open source image editing tool that provides a no-cost alternative to expensive programs such as Photoshop. Topics include the new user interface and tools, the basics of image editing and simple adjustments, advanced techniques using layers and masks, developing RAW images, working with the improved text tool, and preparing high-quality black-and-white images. The most important editing functions are presented in individual, easy-to-follow workshops. A bonus section on the included DVD describes special techniques for web graphics.
