From my favourite writer, John Steinbeck: "East of Eden."
Generally considered to be his greatest work.
This from Wikipedia:
"Steinbeck's inspiration for the novel comes from the fourth chapter of Genesis, verses one through sixteen, which recounts the story of Cain and Abel. The title East of Eden was chosen by Steinbeck from Genesis, Chapter 4, verse 16: "And Cain went out from the presence of the Lord, and dwelt in the Land of Nod, on the east of Eden""
But don't let that put you off. It's a family story (particularly, two brothers) concerning settlers in California in the 1800s.
It's long, but you just don't want it to end.
Steinbeck's skill was in taking pretty serious themes and telling the story with a light, familiar touch.
I'm biased, but I've rarely come across a writer with more interesting relatable characters.
Forget that god-awful film version. It deals with only a quarter of the book, and leaves out the most important character.