What is the theme in East of Eden by John Steinbeck?

Good and evil is at the centre of Steinbeck's masterpiece. Steinbeck alludes to the story of Adam and Eve and their sons, Cain and Abel, extracted from the Book of Genesis in the Bible, to illustrate the theme of good vs. evil in life. In the Bible story, Adam and Eve are created to live in paradise in the Garden of Eden but their sin casts them out. Their sons, Cain and Abel, take different paths, and Cain ultimately kills Abel and is banished to live in Nod, a land east of Eden. Steinbeck believes that all men have both good and evil in them and, although most do not commit the heinous crime of fratricide, all men live east of Eden, where they must struggle with the human condition.