This is my K2. Grapes of Wrath is my Everest. I've started it ~7 times and never made it past 120 pages. Good Luck!
There are much harder works out there. Gravity's Rainbow, Infinite Jest, Finnegans Wake to name but three. Heck, even Walter Scott's novels. That's before we get onto ergodic literarure.
I read the Grapes of Wrath many years ago. I think Steinbeck is more effective in his shorter works.
For me, I took a copy of it with me on a solo backpacking trip. It was the only entertainment I had for a week.
It's good.
Try to get a modern translation if you're not reading in original language.