An interesting and well written book that completely failed at several key points. The basic structure of the novel is that it's a standard piece of literary fiction, with the normal elements of growing up and writing and Europe and affairs, and then half way through it introduces fantastical/horror elements as one person in the story might be an actual magician.
On the positive side, the book is relatively brief and often well written. There's one part near the middle which is a good example of the author's voice:
"My stepmother had begun to lose the nice figure she'd brought to their marriage, but at the same time, she looked both more relaxed and more sure of herself than when I'd last seen her".
Many writers would come up with some variation the first half of that sentence, with varying levels of venom or acidity or acuity. I like though that the author also has the second thought, which is more humane and fair minded and takes in the broader picture outside of his immediate concerns. This pattern occurs frequently through the book, where the author will cover expected beats but will also have a second and more interesting level of thought or insight or consideration. It's not a work of blazing genius, but it does make the story quietly readable and enjoyable. These good points persist through most the story. The bad points of the story are more like sharp, critical failures. There are three of them.
1) The ending. It is extremely abrupt, and little-to-no groundwork was laid to support the ending. You can imagine War and Peace stopping with "and it was all just a dream" to give you an idea of how bad this was. The most charitable interpretation is that a dead, mind reading magician drove the narrator insane, or else completely scared him using illusions and mind magic and his long harbored guilt. Only slightly more plausible endings are "the narrator was always insane" or "the narrator exists inside a hell dimension controlled by his sadistic older brother". All of these explanations require giant leaps of faith and copious head scratching, and are literally the only way that I can make sense of what goes on.
2) The affair. This was less obnoxious, but was still a critical failure in the novel. One of the key plot points is that the narrator sleeps with the magician's wife, and this is taken as a giant betrayal. Which, ok, I guess it is. But at the same time it's like holy shirtballs, every single circumstance of their time together was pushing for this to happen. It was the least shocking thing ever; there are large parts of the novel where it seemed like the magician was actively pushing them to sleep together. At this point I'd call on Mike Pence, Taylor Swift, and Iris Murdoch. If you don't want to have a terrible-idea -affair, don't place yourself in the position to have a terrible-idea-affair. It's basic interpersonal mechanics. But in the story, the 40+ year old magician is like "nope, this is fine" and then gets super offended when the absolutely expected happens. Compare this to another fictional magician love story by the super literary Jim Butcher. Spoiler, but in that series of books, the narrator and his magical study-buddy fall in love, because they are teens and of course duh. And their mentor planned it that way and setup their time together to promote that, because that would be useful to him. Anyway! If Jim Butcher is surpassing you in realistic relationship dynamics, your magician needs to go back to charm school. zing.
3) The Guilt. Finally, there is this consistent judgment through out the book that the narrator is a scumbag and that his older brother and his delinquent friend were vital and full of life and magical and wonderful. And it's just completely dumb. I can understand this judgment as like the narrator's trauma reaction from having to deal with his sadistic older brother while growing up, and that completely skewing his viewpoint, but it's incredibly wrong. But I don't feel like many of the reviewers on GoodReads really understood that, and it's not clear if the author did either, e.g. whether he actually thought that way or whether he meant for it only to be that the narrator thought that way. Anyway! Just for the record, the older brother his friend were both violent morons who played stupid games and won stupid prizes. In the key scene where the older brother gets it, there are just RIRs all over the place. As with the affair, it's the second least surprising thing ever.