One book I'd recommend is Bennett-Levy, et al (2004) Oxford Guide to Behavioural Experiments in Cognitive Therapy. The book isn't specifically about insomnia but it is quite good and includes a good chapter on insomnia which outlines a number of useful interventions.

There are also a couple of books on insomnia that I haven't seen but which sound promising: Treatment of Late-Life Insomnia by Kenneth L. Lichstein (Editor), Charles M. Morin (Editor) focuses on late-life insomnia but most of the content would apply to all ages. It includes a chapter on CT with insomnia. Insomnia: Principles and Management by Martin P. Szuba (Editor), Jacqueline D. Kloss (Editor), David F. Dinges (Editor) appears to be a good overview of the current literature on treating insomnia but isn't specifically about CT.