|If you have attended a Level 1 course through the ITC, look on your ITC Utility CD under the "Technical Documents" heading for the list of reference books. If you don't have that, here are just a few that I like:
Common Sense Approach to Thermal Imaging
by Gerald Holst
You can find it here: http://www.jcdpublishing.com/
Also, any of the Proceedings manuals from the past Inframation conferences are excellent sources of application and science for the infrared world.
Hope this helps, and good luck to you on your quest for Level 2.