From publisher blurb:
What began as an attempt at yet another retro-clone, morphed into something altogether different. Included in this “alternate player’s guide” for Basic Era and compatible games, are alternate rules for classes, races, combat, and spell-casting. Technically speaking, this rules set includes everything you would need to play. However, your mileage may vary on that, and you may either import other rules, or cherry-pick what you like from here.