The face in the frost

Blurb

The Face in the Frost is a short 1969 fantasy novel by author John Bellairs. Unlike most of his later works, this book is meant for adult readers. It centers on two accomplished wizards, Prospero and Roger Bacon, tracking down the source of a great magical evil. The subject matter prompted Ursula K. Le Guin to say of the novel, "The Face in the Frost takes us into pure nightmare before we know it—and out the other side."
This novel was listed in the "recommended reading" list in the first edition Advanced Dungeons and Dragons Dungeon Master's Guide by Gary Gygax. Prospero's practice of studying his book of spells the night before he might need them may have helped inspire the game's requirement for magic users to do the same.