This is a bit of a long shot, but figured it might be worth it.
I’m looking for a work of incest-themed erotica featuring a mother who seduces her son. It’s written from the point of view of the mother, which makes it rather unique for most mom-son incest stories, and it’s pretty well written.
I think there was a workout scene with the two of them in their home gym or something like that, and them getting sweaty was used as a pretense to shower together. I remember specifically the mom comes up with the idea and is wracked with nerves the first time she invited her son into the shower with her. She says something to the effect of “are you just going to stand there or get in?” but she’s so clearly nervous she remarks to herself how forced it sounds even to her.
Eventually she ends up giving him a handjob in the shower after they get over their initial nervousness, and it progresses over the course of a few stories into them having full-blown sex.