The 2 books I have always next to my bed:
1. Luftwaffe Fighter Aces: The Jagdflieger and Their Combat Tactics and Techniques
2. Luftwaffe Bomber Aces: Men, Machines, Methods
Both are written by Mike Spick and are very similary built up, just one is about fighters, other is about bombers pilots.
They are documentaries, but built up bit like adventure books - they take one thing at a time(like Battel of Brittan), then talk how it was, then maybe picks out few better moves or things(or pilot reports). In the end it talks about the planes and the pilots and then moves on to the next place(and everything is by the timeline).
Very intresting, it talks about the German adventages and problems; all the important planes/pilots; tactics etc.