https://nwhyte.livejournal.com/3658188.html

A short sf novel from 1974 about a middle-aged lecturer in an unsatisfactory marriage who distarcts himself by science fiction and flirting with a student. You can get it here. Both activities suddenly get more serious as the world that he is writing about turns out to be real and distant, and intruding on Earth, and the student starts to flirt back. The story ends with restoration of the status quo rather than any change to the frame of reference. It's about halfway between Kingsley Amis and Douglas Adams, and I was so struck by a certain similarity of tone with Hitch-hiker that I wrote and asked Christopher Priest, who knew both Cowper (John Middleton Murry Jr) and Adams personally, if he thought that one had partly inspired the other. (He said no.) ( )

A book I have always admired, because of its central conceit. Everyone has wondered this at some time or another; only Cowper, as far as I know, has actually made a novel out of it.

George Cringe is a middle-aged school teacher, with a less than satisfactory marriage. He is attracted to a younger colleague at the school where he works. As light relief from this stressful life, he is writing a science fiction novel about the planet Agenor, where his hero, the teacher Zil Bryn and his partner, Orgypp, are having problems with an outbreak of giant psychedelic mushrooms.

Meanwhile, on the other side of the galaxy, on the perfect planet Chnas, the teacher Zil Bryn has a happy life with his partner Orgypp, apart from problems centred upon an outbreak of giant psychedelic mushrooms. But Bryn is finding relief from this by composing a strange narrative, set on a mythical planet called Urth, about the deeply troubled teacher Shorge Gringe...

I've not read this recently, but I recollect it being a fun piece of satire. ( )