A strange book, but I liked it. A feature mentioned in the translator's intro is that highly poetic language alternates with ordinary speech throughout the book. It was startling at first, and then I just got used to it. The Christian overtones of the ending might have been annoying, but I just put it down to the general weirdness of the book. In the end, I think the weirdness of the novel is well suited to the strangeness of Alexander's story, so it works. I'm not sure this would be everyone's cup of tea, but it worked for me.
Another interesting note from the Translator's introduction: Before he wrote Alexander, Klaus Mann's first novel was one of the first novel's in Germany to deal with homosexuality openly, and "inspired" his father, Thomas Mann, to write an essay in which he condemned homoeroticism. Since we know from his own diaries that Thomas Mann was a closet case, I'd say this story does not reflect well on him. Certainly puts Klaus's version of Alexander's story in an interesting light.