I'm a great fan of lore books as opposed to textbooks or reference books. Lore books are the ones that contain the things that many people in the field may know, but which they had to learn the hard way, and I like them because they help me learn the easy way.

Miller and Friedman have written a fun and useful lore book, which has helped a lot of electro-optics people (including me) stay out of some nasty potholes. The book is inexpensive, and if you're building or specifying electro-optical systems of any sort, you should own it.

Note added 8/08:
I still think Miller and Friedman is a useful book, but at this point I'd want to qualify my paean above: there's a certain amount of sloppiness in the way some of these rules are presented that keeps it from being a fully reliable guide. (3-1/2 stars)