This book was about him, a military flier, not about combat aviation. He doesn’t give advice about combat but I gather it would be this–stick to the basics, this is safety and hope your number doesn’t come up.
He drank milk instead of alcohol and had trouble fitting in because of that and his obsession with solo sports. He also seems to be a slow learner. I gather he is something of a pariah until he gets a commander who also loves sports.
When he gets his chance he flies more than anyone. When he becomes a leader he insists on commanding from the front. One paragraph has blood spattering from his stump from being rubbed by a hook that allows him to work the foot pedals. He notes that the mechanics had to wipe the blood off the machinery between sorties. This made me think of Darth Vader.
He’s generally respectful of his Nazi leaders but refused to obey their orders that would ground him for publicity or command reasons. He does comment on Göring playing dress-up.
In interviews as a prisoner he derides American focus on speed. He cites his success in the Stuka flying low and slow up till the end of the war. This is the insight that made the A-10 so successful. The other tactical point I got is don’t ‘dodge’ flak. Get in and get out.