I admittedly haven't read a lot of books on photography, but I do frequently read technology books, and Light: Science and Magic is one of the best I have read. Many challenges arise for technical books: keep the reader engaged, don't write a dry treatise, maintain balance between too basic and too advanced and include all the relevant points so the reader can follow the train of thought. The authors manage do all this and impart a great deal of knowledge on how light works in making pictures.
I appreciate their approach of presenting a problematic situation and then giving principles of how to solve the problems encountered. They don't give a cookbook recipe but rather go into details about what the challenge is and explain how to overcome it with both positive and negative examples.
The situations presented tend towards product shots such as might be found in sales catalogs, but this is in no way a limitation. The authors simply use this context to present principles of lighting that are applicable to any type of subject. This gives the advantage of a tightly controlled environment, so the reader can easily reproduce the setup to get hands-on experience and cement the lessons in their mind. The training can then be applied outside the "laboratory" in real-world situations.
In addition to writing a great book, the authors created and hang out in the Light Science and Magic Flickr group. This group is specifically for people to post images inspired by the book with explanations about how they made the image. There are also low-volume, high-quality conversations in the discussion section.
Finally, they run regular challenges based on topics covered in the book. Currently (November 2008) the third such challenge has just started. The idea of this challenge is to use a single light source to illuminate an object but also provide a graduated background, giving depth to the image. The rewards for participation is learning more about lighting with one lucky submitter being awarded a free book from Focal Press.