Mapping and Modding Half Life2
"The book shows, step-by-step, how to create new maps, textures, characters, 3D objects, weapons, audio effects, game action, and much more. Readers will learn how to start out by creating new maps and models and then learn basic techniques of coding to create useful mods. The second part of the book features more advanced techniques as readers learn how to expand their skills and develop more sophisticated models and 3D action. The book also covers other important areas of mod development including creating and managing a mod development team, working with fans, and using skills to develop a professional career in game development."
The book is from the same publisher as Paul Marino's Machinima Book and should be available from March this year. Though, you never know.