I mean real books and not comic books. I read my share of the latter, for sure. I was a dinner table reader. The nice thing about comics is they would lie down flat on the table to give me some entertainment at meals.
As for real books, my reading classmates and I thoroughly enjoyed the Three Investigators detective series, with Pete, Jupiter, and some other boy. I couldn't get enough of those books. Unfortunately, the ones I was missing were checked out of the library. These were somewhat spooky mystery stories, such as "The Mystery of the Screaming Clock," which kind of scared me at that young age, but the stories always ended with a natural explanation. Yes, that does sound like Scooby Doo and the mystery bus, only with more literary substance.
I've never read a single Hardy Boys mystery. Those seemed to me more like the typical gift from a well-meaning Uncle which sat on the shelf and never got read.