Probably the best place to start regarding information on the AVG is its website:
http://www.flyingtigersavg.com/At least two members of the AVG, Chuck Baisden and Frank Losonsky, frequent the forum on the site and are a wealth of information. In addition, the website lists numerous books about the AVG, including ones by its members.
I've had the honor of meeting some members of the AVG and 23rd FG who served with "Tex" Hill, although unfortunately I never met the man in person. However, many years ago I wrote him a letter and he followed up on it by calling me one evening, just out of the blue. That right there is an indication of the gentleman he was.
Mark