Choose Your Own Adventure books
The concept of these books is pretty simple. The reader assumes - some later series added minimal character generation rules - the role of the main character in the story and the decisions made at certain points of the story determined the direction of the story. The reader usually read between half of a page to several pages and then was given a list of choices. Following the choice would lead to an outcome and you would then arrive at another list of options.
This series of books was widely available in my local area. The library had a whole section of them in the middle school, the book fairs at school always had several of them for sale, and the weekly readers from grade school would have several of these listed in them on a regular basis.
When the gaming group was not gaming, we often did other things in our spare time. One of those activities was reading through one of these books. I read a ton of these things as a child and also branched out into other series such as Pick a Path to Adventure, Lone Wolf, Sorcery, and Zork just to keep the list small. Of course, we would usually buy different books and then swap them when we were done reading them. I remember keeping a notebook that would list the choices made in the book and whether or not they led to victory or defeat. I would pull these books out at a later date and read through just the victory choices so I could have a smooth read without backtracking after defeat.
I believe these have somewhat come back into some level of popularity now. I would read new ones today but I would probably want one of the series that included a limited form of character creation before beginning the read. Of course, I may still have a small box of these in storage at my parents. I wonder if that notebook with all of the solutions are there also? Hmmm....