While we're at it I can also recommend Mephisto by his son Klaus Mann. Klaus wrote over a dozen works but Mephisto is his most widely acclaimed work. It was also made into an academy award winning film in 1981. Following is a blurb:
Hendrik Hofgen is a man obsessed with becoming a famous actor. When the Nazis come to power in Germany, he willingly renounces his Communist past and deserts his wife and mistress in order to keep on performing. His diabolical performance as Mephistopheles in Faust proves to be the stepping-stone he yearned for: attracting the attention of Hermann Göring, it wins Hofgen an appointment as head of the State Theatre. The rewards – the respect of the public, a castle-like villa, a place in Berlin's highest circles – are beyond his wildest dreams. But the moral consequences of his betrayals begin to haunt him, turning his dreamworld into a nightmare.
Something you may not be aware of is that his daughter Erika Mann was also a writer and actress who married W.H. Auden in order to obtain British citizenship.
Cheers.