I have actually tried not to write books that are connected.
Truth and Consequences? Not supposed to be a Hearts of the South book. Yet Kathleen and Jason insisted it was set in my fictional Chandler County, and of course, Tick followed. I don't think he can help himself.
Finally, I just gave in. Several related books followed. Yes, it's a series, but it's one of those where you could pick up one book and you wouldn't have had to read the others for the book in question to make sense. Stand-alone yet connected books.
And here's how I get sucked in.
I'm rereading two manuscripts, A Formal Feeling and Anything But Mine. There is a minor, minor, minor character in A Formal Feeling. She appears in one or two scenes, in which the hero makes a pivotal choice. She goes inside her house, closes the door, hero walks away.
Only as I'm reading tonight, I'm wondering what happens once she closes that door. Her actions in those scenes are out of character (or so she claims). What pushed her to the point that she'd act out of character?
I can almost see how another story could unfold from what goes unsaid in those two scenes.
Kinda like a weird, writer's version of Six Degrees of Separation.