We've got your back. With the Tough-O-Meter, you'll know whether to bring extra layers or Swiss army knives as you summit the literary mountain. (10 = Toughest)
(2) Sea Level
Steinbeck's writing style is straightforward and mostly free of million-dollar words (or even ten-thousand dollar words), so we don't think you'll find the book too hard to trudge through on that level. That said, sometimes he asks you to read between the lines rather than telling you exactly what's on his mind. For example, some of his references to his fears about nukes are more on the subtle side, requiring that you be, you know, awake in order to pick up on them.
Also, there's a lot of rough (to put it mildly) language once he gets into the Civil Rights Movement, and you'll have to endure free and frequent use of the N-word during those chapters as he reports the conversations he had while traveling through the South. Apart from that, though, the language is on the lighter side, difficulty-wise.