Upvoted. I actually had a remarkably similar experience reading Lewis. Throughout college I had been undergoing a gradual transformation from "real" Christian to liberal Protestant to deist, and I ended up reading Lewis because he seemed to be the only person I could find who was firmly committed to Christianity and yet seemed willing to discuss the kind of questions I was having. Reading Mere Christianity was basically the event that let me give Christianity/theism one last look over and say "well said, but that is enough for me to know it is time to move on."