There are some books with an LED section in them. Truth is, your very best resource for accurate, up to date info on LEDs is... right here on the Farm. These people collectively run one of the best testing facilities for LEDs- or anything else for that matter- anywhere. You get the straight scoop from people running the gear, usually with pics to show what they're talking about. It's updated literally minute by minute, you just can't get this kind of in-depth yet timely information from a book.