“Non-Germans” Under The Third Reich - Diemut Majer
Race and the Third Reich - Christopher Hutton
The Nazi Ancestral Proof - Eric Ehrenreich
The Gestapo and German Society: Enforcing Racial Policy 1933-1945 - Robert Gellately
Gellately's book Backing Hitler: Consent and Coercion in Nazi Germany also mentions the racial thought and several degrees made.
Do you know of any other books that deal with specifically the racial side of the Third Reich?