Marion Zimmer Bradley is rapidly becoming one of the best writers in our field. Book by book … she has been increasing her command of the craft and art of writing. The [deepening] of her characterization and the widening of her grasp of background, along with the increasing honesty and inventiveness of her plotting, are all joyous developments to behold.

Her "Darkover" stories are her best known ones, of course. And they depend on psi-effects to a major extent—a subject which I don't normally enjoy very much. Frankly, while I found the early Darkover novels fairly good reading, I wasn't much impressed. Now I look forward to each one with the keenest anticipation.

The latest is The Forbidden Tower…. And it lived up to my anticipation in every way, despite the fact that much of the story involves a sort of love relationship among a group of people—something that becomes unendurably treacly in the hands of a lesser writer.

This is a direct sequel to The Winds of Darkover. In that, the Terran Andrew Carr was drawn into a crisis between Darkovian people and another race that had learned to control the psi-crystals that are the source of Darkovian power. He rescued a Keeper (a sort of virgin priestess), and at the end was riding off with her toward his new home on Darkover.

This book picks up immediately with their intended marriage. (pp. 170-71)

Somehow, the characters—even many of the lesser ones—become very real. And the background of Darkover—by this time a most fascinating world—is deepened. Psi, which is too often just a magic gimmick, becomes more and more a believable alternate body of science; each book recently has developed more and more of the understructure of this; as Bradley uses it, it no longer bothers me, but becomes a truly fascinating alternate.

I found it splendid, and can't recommend it too highly. (p. 171)