The Archaen Codex (1992)

 From the back cover:

"Lost spells and skills, artifacts and magical treatises, tidbits of history forgotten since the days of the Archeans - these ancient secrets have now been brought to light for the first time in The Archean Codex. In this book, you will learn the origin of the Black Savants, the technomantic techniques of the Neurians, the summoning spells devised by the magician Mordante, and the nature of the ruins in which these and other wonders of Talislanta's greatest magical era may be uncovered. So pack your research notes; the treasure hunt has begun!"

 From the web:

 Day 142: At long last, success!

With much difficulty, we finally located the true entrance to the ruins and defeated the magical wards guarding the ancient Phaedran burial chamber. Inside, among other artifacts, I have discovered a crystal-bound tome that appears to have been written by the master Koraq himself! If this book is indeed his Theory of Magic and Anti-Magic, I am certain my understanding of the nature of magic is about to increase greatly...

Lost spells and skills, artifacts and magical treatises, tidbits of history forgotten since the days of the Archaens - these ancient secrets have now been brought to light for the first time in the The Archaen Codex. In this book, you will learn the origin of the Black Savants, the technomantic techniques of the Neurians, the summoning spells devised by the magician Mordante, and the nature of the ruins in which these and other wonders of Talislanta's gratest magical era may be uncovered. So pack your research notes; the treasure hunt has begun!