The excitement described by Carey Bunks when he first beheld the GNU Image Manipulation Program (GIMP) in 1996 is palpable when you hold Bunks's new book in your hands. The phantasmagoric image on the cover of Grokking the GIMP: Advanced Techniques for Working with Digital Images melds a photograph of the moon's surface from a high orbit with an apparent solar eclipse by the earth. A penguin floats discretely in a hot air balloon between sun-earth and moon. Is the sun-moon-earth image a bit of the penguin's imagination? Is it a piece of GIMP artist/developer Tuomas Kuosmanen's imagination? Maybe it is really a credit to the visionaries at New Riders who have produced an art book to suit the computer how-to market.

"Grokking" is a Robert Heinlein-ism for "appreciating," and docent Bunks takes us through the museum of computer art and method as he demonstrates the features of the freely redistributable package. The contents follow that path set down by many other how-to tech book authors: tutorial, a taste of image theory, working with the independent features of GIMP (layers, selections, masks, and colorspaces) before advancing to compositing and rendering, and ending with a short review of Web-based applications of image manipulation.

The book's strengths are Bunks's obvious passion for his subject, his mature didactic style, and the wonderfully spacious design and breathtaking color-on-every-page strategy that allows him to beautifully frame GIMP features at their best. The most notable of his many case studies is the "Panorama" project that glues a series of laterally overlapping narrow-view photographs of an architecturally interesting room into a single, stunning, wide-angle panorama of the whole. Bunks documents each step in the transformation and describes the required geometrical, hue, and brightness adjustments needed to warp and blend them together.

Look again at the cover, but not literally. Ignore the unphysical details. Rather, imagine the mind's capacity for juxtaposition and GIMP's power for actualizing this visual synthesis. In form and content, Bunks and New Riders have shown that the possibilities for the tech book are far broader than previously imagined. This is an eye-opening contribution, indeed. --Peter Leopold