Below are a list of books on thermography all of which I recommend, the first three are essential for anyone serious about working in the field of thermography. For other products see our products page.
Common Sense Approach to Thermal Imaging by Gerald C Holst (essential reading)
Practical Applications of Infrared Sensing and Imaging Equipment by Herbert Kaplan (essential reading)
A Practical Guide to Infra-red Thermography for Building Surveys published by BRE
Building thermography by Davide Lanzoni
Infrared thermography: electrical and industrial by Davide Lanzoni
The Infrared Handbook by Wolfe & Zissis (essential reference book)