The Second Grimoire of Pharesm the Bright-Eyed

From the introduction:

The rules contained in this booklet are major modifications to the current editions of the DUNGEONS & DRAGONS Basic Set, Expert Set, and Companion Set (the latter has just been published and is not much dealt with in these rules as that level of play (15th to 25th level) will probably never be reached) rules which are published by TSR. Possession and understanding of at least the D&D Basic Set Rules is required to understand and use the modifications presented herein.

User summary:

These house rules for "The Gamer's Lair D&D Campaign" provide an interesting glimpse into the once-very-common practice of playing "Variant D&D" (or "VD&D"), an early precursor to the more recent practice of retro-cloning.