[powrtoch]

Re CYOA/RPG combo, I believe you're referring to the Fighting Fantasy series: https://en.m.wikipedia.org/wiki/Fighting_Fantasy

There's a fun confusing fact about that series, which is that Steve Jackson was one of the creators and frequent authors. "Oh, Steve Jackson, the creator of GURPS and Munchkin!" you're saying. Nope, different Steve Jackson. But wait! That Steve Jackson did come along later and author a few books in the series. So now a bunch of those books have "Steve Jackson" listed as the author, and there's no way of knowing which one it is without googling.

[lsaferite]

There is also Fabled Lands (https://en.wikipedia.org/wiki/Fabled_Lands) which was pretty cool because you could make choices that could take you to another entire book if you owned it.

[PhasmaFelis]

There were quite a few RPGs-in-book-form. I had a Middle-Earth one that involved delving solo into the Mines of Moria. But Fighting Fantasy seems to be the best-known, and may have been the first.