My friend claimed he'd written a CYOA book. Is this a real thing, or did he fool me?

Back in the 60's, my friend wrote a book that had a chapter with a set of choices for what the characters could do next. The reader would pick "them" and go to the correct chapter, and so on.<br><br>He claimed this was a Choose Your Own Adventure, but I'm not familiar with the term, and my wife and mom have never heard of it either. How did he fool me?