This is the 1981 edition of the D&D Expert Rulebook by Dave Cook, which was sold as a counterpart to the Moldvay D&D Basic Set.
Product History
The Dungeons & Dragons Expert Rules (1981), by David "Zeb" Cook, was released simultaneously with the second edition Basic Rules (1981) in January 1981. For the first time ever, it offered the opportunity to achieve levels 4-14 in TSR's... [click here for more]