It was generally anything opposing the NS Regime. Left Wing literature being a prime example, since Social Democrats where one of the largest oppositional forces to Hitler. Socialists and even more moderate Conservatives where opppsed to Hitler. Famous Communist Rosa Luxemburg and Konrad Adenaur, kown Moderate Conservative and first Federal Chancellor being prime examples. Anti war art, Jewish Literature, Pacifist art and literature anything really that didn't glorify Germany. I don't think there was much, there probably was a little, Homosexual Literature as at the time the issue was still socially "Immoral" and had subsequently rather limited reading material about it that one might consider good.