ABANDONED. A woman whose husband is having an affair with get best friend and she decides to try to "keep them both"

[Robin]

I read this within the last six months but I'm afraid I don't know when it was published (I was lent a paperback copy)
It wasn't very good but it's driving me crazy not to remember the title.

The plot concerns a woman who illustrates books. Her husband is some kind of academic and has had affairs before. She discovers that he is sleeping with her best friend but (and I think this is supposed to be a surprising twist) she decides she wants to remain married to him and friends with the friend. The story is basically her trying to drive them apart and waiting for it to fizzle out.
I think the friend is called Maddie. Unfortunately I'm not good at remembering names.

Any ideas would be very welcome.

[Kris]

Robin left the group. Moving to Abandoned folder.

Robin (OP) last posted in the group in April 2019.