If you want to read about Ernst Udet, two books are indispensable. Udet wrote his own episodic biography entitled Mein Fliegerleben, published in 1935. It has been twice translated into English. In 1937 a British edition, translated by Kenneth Kirkness, came out as Ace of the Black Cross. You may be able to find this old book via used book outlets or websites. However, in 1970 a new translation by Richard K. Riehn was published in the US entitled Ace of the Iron Cross. This came out in several paperback editions and should be easy to find on ebay or from used book outlets. I think the translation is very good.

Udet wrote (or perhaps dictated) a rather short and propagandistic wartime paperback memoir entitled Keuz wider Kokarde, published in 1918. It is very hard to come by and is rather expensive on the used book market.

The best biography of Udet was written by Armand van Ishoven, entitled The Fall of an Eagle; The Life of Fighter Ace Ernst Udet, (William Kimber, London 1979,ISBN 0 7183 0067 X). It really is a superb biography, well researched and nicely illustrated.

And of course the debate goes on about the DVII. Was it red or not?