This book follows a biography model, following the life of Simmu, from the inexplicably strange circumstances of his birth, through his childhood, adventurehood, his crowning successes, and through to his final fate. While following this story, we also follow the story of several other characters closely associated with Simmu, such as Zharak.
Overall, the writing proceeded thickly and formally, feeling mildly archaic even for 1979. Fortunately, Tanith knows how to work with this thickish prose, pulling it like taffy to extrude the tale. And what an improbable tale it is, full of overpowered characters who successfully prove that overpowered actions create overpowered results, generating overpowered reactions, which generate more overpowered results, and so one. When the story centers around the fundamental powers of of the universe, such as Death and the Prince of Demons, overpowered ceases to be a meaningful term.
The book is also an "adult" fantasy novel, so sexual situations about. To be clear, the book is not explicit, but it is forthright. It contains sexual situations of all sorts, some of which are gender bending, and some of which are jaw-droppingly outlandish. Lee can and does push sexuality in new and unique directions.
This was my first Tanith Lee. I liked this well enough to read more of this series, but not so much that I'll rush out and buy some right now.