First the Choose Your Own Adventure books. It was groundbreaking (at least as far as I knew). I found a couple in an old bookstore a few years ago and snapped them up immediately ... lost jewels of djibouti or something was one of them ... in storage now.
Then came Fighting Fantasy, which as far as my knowledge serves was basically the anticedent to D&D. Same as CYOA, except we had skill and stamina levels ... and rolled dice whenever we ran into a bad guy.
I don't remember any of the FF books, but would LOVE to run across them again. The main reason I don't remember them is because I tainted my memory by writing my own!! I was a kid, given, but I still have them (in storage), and was especially proud. Still am. I completed one called "Mission Morson", and followed up with "Mission Lancarren". As a young'n, I happened to make them unnaturally difficult, but they were still fun to try.
Mission Morson centred around a castle and the forest behind it. The forest also had a small tunnel system underneath it which was basically a third location. There was some underground town in a big cavern, too, but my memory is hazy, there.
Then there was Mission Lancarren, which started at the town of Knirrankee and wandered around a bit before heading along a track which followed a river, and eventually headed into mountain ranges, amongst which was the big test, Mount Lancarren. The tunnels and chambers in there were three-dimensional, I had to find a big hunk of polystyrene foam and stick coathanger wires in it so that I could map out passages that sloped, rising and dropping levels, so that I could know the directions to use. A special time in my life

I went on to commence Mission Amman, which was going to head through various town and farmland, but only got a dozen pages in before ... umm ... growing up

But it was off its nut at the time! Keys and monsters and treasures and staircases and oooh somebody stop me!
Mission Morson I first wrote in a schoolbook and later typed up, while Lancarren remained in an exercise book, and Mission Amman was commenced in a big diary.
I even wrote a computer program which could automatically suggest page numbers for me (you know how they send you to different pages based on the decision), which made things easier, on the old Commodore 64.
Then I translated the entire Mission Lancarren (my biggest production) into a QBasic computer game. The whole thing worked and I loved it!
I translated the files only a year ago from Basic A on 5&1/4 to QBasic on hard disk ... took a bit of work ... and then found that many of the files (pages) were missing

One day I'll fix it up!
Tell yers what, if I ever get either of them out of storage, I'll present them here as a game, type in a page and allow yers to make the choices, and go on from there

Anyway, it was exciting stuff.