Goodreads Summary: Chthon was Piers Anthony’s first published novel in 1967, written over the course of seven years. He started it when he was in the US Army, so it has a long prison sequence that is reminiscent of that experience, being dark and grim. It features Aton Five, a space man who commits the crime of falling in love with the dangerous, alluring Minionette and is therefore condemned to death in the subterranean prison of Chthon. It uses flashbacks to show how he came to know the Minionette, and flash-forwards to show how he dealt with her after his escape from prison. The author regards this as perhaps the most intricately structured novel the science fantasy genre has seen. It was a contender for awards, but not a winner.
A lot it is said about this book about its narrative structure, starting in the "present" and then doing flashbacks explaining some point (sometimes) and then showing the future in "flash forwards". The thing is, "flash forwards" don't feel like "flash forwards"; the simply appear as if the future is the present and the present became a flashback.
Also, the flashbacks sometimes are not explanative and a bit too long. The very first one doesn't explain anything about the current state of the story, and it is so long you have to wonder if the story actually moved back or it is talking about something else.
There is also some weird jumps in the story that made me feel like I skipped a whole page for some unknown reason, and I had to track back, see that I didn't skip anything and the story simply did a (small) jump in the plot.
The characters are really bland. One of the topics, the fact that a race actually feels hate as love (and no, that's not a spoiler, 'cause you don't know who I'm talking about), is actually really bad explained and explored -- and the weird fact that, as the author puts in the post words in the end, that was the origin of the book.