I read somewhere that the best thriller writers make you feel like you're the detective, not just watching one. That guy at the library must have known that trick. I bet he showed you how to pick up on small details that authors plant on purpose, stuff you usually miss. Once you notice those breadcrumbs, thrillers hit different. You start second-guessing every character and their motives. Feels like you're actually solving the puzzle instead of just waiting for the end.