I teach this book. It’s the details. The everyday life that is captured in the book up until the murders that gets me. Like how the neighbor girl was going to learn how to make a cherry pie. How Mr. Clutter paid for everything in checks, etc. In case OP didn’t read the dedication page, Capote’s childhood friend, (Nell) Harper Lee, helped with researching the book. She went on to write To Kill a Mockingbird. Capote is the basis of Dill. Capote has been credited as creating the true crime novel genre.