To legally use a 5.8GHz video transmitter in the U.S. you need at least a Technician Amateur Radio license. It is not a hard test, but I wanted some study aids to make sure I only had to take the test once.
A little bit of searching on Amazon led me to The No-Nonsense Technician Class License Study Guide (2014 edition): For tests given starting July 1, 2014 [Kindle Edition] for a very reasonable price.
It is a very good book covering only what you need to know to pass the test without a lot of fluff that many of the other study books include.
I rate this book a 10 out of 10 and recommend it to anyone who wants to quickly learn what it takes to pass the Technician license.
I passed my test only missing 2 questions after reading this book twice and using an iPhone app to take around 100 practice tests.