What is the theme in Lord of Light by Roger Zelazny?

Circularity is a central theme in the book. The Hindu religion upon which the "gods" of the planet in "Lord of Light" base their authority is based on an idea that life is circular or cyclical in nature. Life does not begin and end at birth and death, but the soul is reincarnated in a series of new bodies. A person who lives a good life can be expected to be reincarnated into a higher social position while a person who has been sinful might be reincarnated into a lower class or into the body of an animal. Thus life is a series of cycles with each ending also a new beginning.