I write mysteries. I had two readers decide one of my characters was the killer. He wasn't (but might have been). Having two readers take the time to consider who the killer might be seemed like success to me. Or, put another way, reader engagement defines success for me. I mean really - what are the chances of any of us getting trad published, and even if that miracle happened, what are the odds we would sell more than a few books? So fame and fortune ain't coming our way. What might come our way? A few readers who care enough to spend some time with our novels. That's enough for me.