I would suggest that a biography that fails to cover the personal beliefs of its subject in-depth, and merely limits itself to commenting on his military career is really a military history, and not a biography.
Also, and this is my personal opinion only, any biography of a WWII-era German that I would care to read ought to first detail "what they knew, and when they knew it", and also their connections to the Nazi party. But I understand that a lot of history buffs don't feel the same way, and I shan't disparage them for that.