This short novel was an excellent read.
The character of Arthur Norris, a worldly, likable scoundrel, is vividly and engagingly portrayed in Isherwood's limpid style. The narrator is a rather bland fellow, and constantly reminded me of I Am A Camera, the title of a play based on Goodbye to Berlin, another work of Isherwood's.
Other characters are equally well-portrayed, and I understand what made Isherwood's depiction of late Weimar Berlin so universally acclaimed. He has a gentle but apt way of describing scenes and dialogue.
I saw others complain about the "vague plot", but I rather think this a strong point of the novel; sure, it's no suspense mystery! But Isherwood skillfully interweaves multiple sub-plots -- Baron von Pregnitz's predilections, Norris and the Communist Party, Otto and the Nazi brownshirts, and the limited angles of Helen Pratt and Frl. Schroeder -- and they all add up to an excellent landscape portrait of that wondrously doomed era.