Is Lord of Light a story about good and evil. Is Sam the "good guy"

This depends on the context of "good guy". Sam is a con-man of sorts, using trickery and deception to fight and escape his enemies. He also has the god-like ability to control electromagnetic forces, but he resists being formally recognized as a god by the others. He is executed once by the gods for his opposition, but manages to survive by transferring to another body. Later he has his soul transmitted into space, but is drawn back into a body after 50 years by Yama to continue his battle against the gods. Sam has been romantically involved in the past with the goddess Kali when both were in different bodies. He has fathered many children, including Tak, the keeper of the archives in the celestial city.