The Spellcaster's Bible (1979)

From the cover:

"A Book of Spells for use in Fantasy Role-playing Games"

Presents 15 levels of spells for use in games similar to the Original Dungeons & Dragons.

On some copies of the first printing the inside cover is stamped (not printed) "Some of the material within this book is inspired by and based upon material from "Arduin Trilogy" and other works by David A. Hargrave ©." This is printed on the inside cover of the second printing.

In the introduction of the first printing 10 mages are listed as having used spells in this book. In the second printing there are considerably more.

The authors are uncredited even though the illustrator is listed.