|The Silent Wife|
There was considerable psychological theory- Freud and Adler, in particular. Both Jodi, the protagonist, and her "husband" of 20 years had serious issues from their childhood and it seems that they were just playing out their parents' mistakes.
There were some surprises, but also some dead ends. Rather interesting and gets better on reflection.
The author, Susan Harrison died of cancer, at 65, before the book was published. She lived in Toronto.