As I was writing the Chris Coulter stories, I threw in a reference to an affair Elizabeth had had the prior winter and not told her husband about. It wasn’t much of an affair–just a blowjob–but the fact that she hadn’t told him stuck in his craw. To make even a simple reference required figuring out at least a little bit about the affair.
Later, the idea intrigued me. So much of erotica is about young (teen or college) adults, that I liked the idea of a main character who was much older, and much more sanguine about non-traditional relationships. Thus, Bob Reynolds came into being.
That led to an arc. I wanted Bob and Elizabeth’s relationship to progress from that first unexpected blowjob to them finding an equilibrium which worked for them. I originally did that in three short stories (which are still available on some sites, but not what I promote anymore). A Good Neighbor collects them together and adds some bonus scenes to flesh out the full story.