I am quite proud of myself that I managed to finish Gantenbein. I never read anything by Max Frisch before and to be honest, it was quite exhausting. Personally, I would describe his writing-style as above average, or even elaborate, so this is no book you can read a couple of pages of just before going to bed. If you want to be able to follow, you have to focus. All the time.
Plot-wise I don’t know what to tell you. There is no such thing as a "real" plot. There are several narrators through which Frisch is trying to explore different possibilities of life. For example, there is one character who has had a one night stand with a married woman and the next day he is at the airport and has to decide whether he should fly home to his own wife or if he should stay and try to start a relationship with his affair. And then Frisch just splits this person by writing that one flies home and the other stays, exploring both possibilities, but neither of them are final. The most typical sentence of this book being "let’s assume that …" and then fill in anything you want.
I once read, that in Gantenbein Frisch is trying to process his pretty intense love affair with his fellow writer Ingeborg Bachmann (and that she was not amused when she read the book), but, well, I don’t know either of the authors well enough to judge that.
The first 100 pages were really confusing and sometimes a struggle to read, because Frisch invents characters, just to give them up five pages later, but as soon as you get used to the style of Gantenbein, it get’s interesting.
Bottom line: if you are interested in exploring the possibilities of alternative writing styles (and not so much in plot), then Gantenbein is probably an inspiring read for you!