The Necromican (1979)

An unlicensed booklet of new spells for the Original D&D game created by two artists who would later work for TSR: Erol Otus and Paul Reiche III (with Mathias Genser).

From the Front Cover:

A book of spells compatible with most fantasy Role-Playing Games

From the Introduction:

This book of spells is not intended to stand by itself, or replace other fantasy role playing game spell lists. Rather, it is intended to supplement the many spell lists in existence, and provide a greater variety and selection for the players. It does not offer an alternate spell system; rather, the spells should be adapted into whatever spell system you prefer. The levels given for the spells are based on our own playing experience, however, it is the privilege of the individual games masters to change the level of any spell so that it will better fit into their own universes.

From Necromican Advertising:

Tired of casting the same old spells? Amaze your friends and dispose of your enemies with well over one hundred new magical spells in, the NECROMICAN. Another fine book from FANTASY ART ENTERPRISES.