The story takes place over an extended period of time and tells the tales of several different characters and how they relate to dying, death and immortality. The common thread is the Lord of Death and how humanity perceives him. There is also the side story of how he interacts with the Lord of Night and the demons. The entire series has a mythic quality, like these were the tales of some long lost culture.
The books in this series are: Night's Master, Death's Master, Delusion's Master, Delirium's Mistress, & Night's Sorceries.
You could read the first 3 books out of sequence and not have any spoilers. Don't read Delirium's Mistress until you have finished the first 3. The last book is a collection of short stories and can be read at any time, but it is assumed that you are familiar with the mythos of the flat earth.
The androgynous Simmu, (he actually could change body forms too), the son of a lesbian queen and, for lack of a better word-- a corpse, was adapted by demons after he was left to die in his mother's tomb. He later meets Zhirem, a boy made invulnerable at the cost of his mother's beauty. The novel addresses their tortured love story in the context of the Demon Lord's mischievious plans to entertain himself, and the Death Master's fight to preserve his supremacy over humans.
Character development was excellent in the case of Simmu and Zhirem. You could read into why they ended up doing what they did, but you could never guess what they were about to do before it happens. Simmu gains immortality and becomes the King of Simmurad (City of the Immortal). Zhirem, the invulnerable, becomes th! e greatest sorcerer in the world, but was directionless until he was taken up by the Death's Master to take on and destroy Simmurad.
The other characters in the story are no less fascinating. Simmu's mother, Narasen was inflicted with a curse by a spurned sorcerer (would-be lover), but her cleverness saved her. Unfortunately, she was felled by treachery in her moment of weakness. Having struck a deal with the Death's Master, she was bound to serve him as the undead. Lylas, the witch, was the Death's Master's handmaiden. Her schemes drive the story forward. Kassafeh, Simmu's wife and the daughter of a sky elemental, was the key to Simmu's immortality. However she finds herself trapped in her immortality. Ironically, she breaks out by betraying Simmu, thus becoming the key to the destruction of Simmurad.
The other questions addressed include, why do people chose to do good, to the point of becoming saints? Is it because they are afraid of being evil? What is evil? ! And so on...
The story is of course, a LOT more complicat! ed than that. After all, it is about how unusual people dealt with unusual circumstances. I totally loved it. It's a great example of Tanith Lee's work, it's brilliant and if I had more space, I will keep on babbling on about how wonderful this book is.
If you've never read Tanith Lee's stuff, this could be a great intoduction for you.