SOLVED. Adult British Thriller Contemporary. Characters are part of a London-based therapy group led by male therapist. Spoilers. [s]

[Radha]

The characters are part of a London-based therapy group, led by a male therapist. It turns out that one of the members has an agenda: she's out to avenge her father, who had an extra-marital affair and was killed by his adulterous lover's boyfriend (I think).

She's tracking the woman who had the fling with her dad--and ended up costing her dad his life, in addition to wrecking her family. So the daughter ends up killing the adulterous lover, who's also in the therapy group.

[Kris]

Radha, around what year did you read this book?

Why are these people attending the therapy group (e.g., different addictions)? How many in the group?

What are the main characters' jobs?

Can we add more details (no spoilers) to the topic header? What key event happens early in the book?

[Kris]

A guess - Die of Shame by Mark Billingham?

Google Books preview: https://books.google.com/books?id=yQN...
There are different cover images.

Google search of Goodreads:
site:goodreads.com "thriller" "london" "therapy group" "therapist"

[Radha]

Kris, thank you. I saw both your messages just now, and you've solved it before I could answer your questions from message 1. The book I'm looking for is indeed DIE OF SHAME. Thanks again.

[Kris]

Great! Glad you found your book, Radha.

[Radha]

Thanks to you.