[Lagarto]

I don't want to drag this argument on, but I doubt the fact that Schiffer's book on JG 5 is 'elderly' and general has anything to do with its affordable price. Either way, it's the only book of that kind on JG 5 in English, so it's always better than nothing.
The "Mediterranean Air War" vol. I by Christopher Shores (560 pages, hardcover) is neither outdated nor general; it can be bought at Amazon for some $40 and delivered free. "Day Fighters in Defence of the Reich: A War Diary, 1942-45" by Donald Caldwell (424 pages, hardcover), also published this year, is even cheaper than that.
I can't comment on JG 2 vol. I, but I do own JG 4 vol. I, which is barely some 230 pages long, big format (which has no special appeal to me) but also big font and double-columned text with large spacing, for a staggering $80 + shipping. No offense but I also had to work hard to earn those 80 bucks, and I had mixed feelings when I received my copy.