Personally I am not a fan of Schiffer Publishing. Their pricing is too savage.
Still every now then when I think an outstanding title is published I do weaken and buy it.
Luftwaffe
JG7 - The World's First Jet Fighter Unit 1944/45, by Manfred Boehme. To my mind the best book on the subject.
Allied
America's Hundred-Thousand, by Francis Dean. This book in incomparable when it comes to information on US Fighters. Without peer.