Series of Adventure books by Joe Dever. The books functioned as a single-player roleplaying game, complete with combat and skill checks. In general, they were a choose your own adventure style book, which presented different choices at the end of every page, with instructions to turn to a different page depending on your choice until you got to the end. Combat was resolved by randomly pointing your pencil at a page of numbers (no peeking) and comparing that number to a chart, along with your combat advantage/disadvantage.

Well, I found out HTML tables don't work on E2...

Lone Wolf