A valuable contemporary record of Mengele's character and performance during his stay at Auschwitz is the "Evaluation of SS Captain Dr. Josef Mengele," dated 19 August 1944, prepared by the Auschwitz SS Physician's Office. (Original on file at the Berlin Document Center.) The report is very flattering:
Dr. Mengele has an open, honest, solid character. He is absolutely reliable, upright and straightforward. He does not manifest any weakness of character, bad tendencies or cravings. His emotional and physical make-up is outstanding. During his period of service at the Auschwitz concentration camp, he applied his practical and theoretical knowledge to combating severe epidemics. With prudence and persistent energy, and often under the most difficult conditions, he completed every assigned task to the complete satisfaction of his superiors. He showed himself capable of handling any situation. In addition, he used what little free time he had to ardently further his education as an anthropologist. His tactful and modest deportment is that of a good soldier. Because of his demeanor, he is especially well liked by his comrades. He treats subordinates with absolute fairness and requisite severity, but is nevertheless exceptionally admired and liked. In his behavior, work record and attitude, Dr. Mengele shows an absolutely solid and mature outlook on life. He is a Catholic. His speaking manner is spontaneous, uninhibited, convincing and lively.The personal evaluation went on to note that Mengele had "contracted typhus while conscientiously performing his duties as a physician at Auschwitz." It listed the awards he had received for bravery and outstanding service, and concluded that he was worthy of promotion.
I got this from "Lessons of the Mengele Affair" (article which I posted already).