The First attempt at turning Fighting Fantasy into a full rpg.
Before the Advanced Fighting Fantasy book was published, Steve Jackson put out a set of rules entitled Fighting Fantasy The Introductory Role-Playing Game (Puffin, 1984).
This book has all of the rules from the well known gamebooks plus extra rules for dealing with common adventuring situations (losing weapons, listening at doors, opening chests etc, things that would otherwise be handled by the text of the gamebook) as well as advice on games mastering etc. There are expanded sections on running bigger battles (ie with a party of adventurers rather than the typically solo adventurer from the gamebooks). There are also two adventures provided.
There's enough for simple dungeon bashing. But soon on it's heels came The Riddling Reaver (Puffin, 1986). This is essentially a mini campaign of four interlinked scenarios all revolving around the eponymous wicked Reaver character. However, this book also brings in extra rules which fill in the gaps from the first. There is variable weapon damage, reactions to injury, unconsciousness and death. And advice on running games in the wilderness. But what makes this book invaluable to a GM is the section on magic and spell casting. It's minimal (there are only ten or eleven spells if I remember) but it takes the claim that this is a proper rpg into the realms of credibility. Add to these two the marvellous Titan (a world source book), Out of the Pit (aka a monster manual) and you're off!
A great addition to these in my opinion is Steve Jackson's Sorcery Spell Book. This is a book written for the Advanced version but is really useful as an alternative magic system to that presented in the Riddling Reaver. The great thing about this book is that each of the spells has a proper name but also a three letter abbreviated form. This short form in intended for use by the players literally to shout out during play! What fun.