Please. Being considered a literary classic doesn't mean anything. I do agree that his ability to describe the surroundings was impressive. Maybe I got distracted by his mention of the Steinbecks in the story. I was trying to figure out who was the narrator and whether the Steinbecks were going to be a bigger part of the story. (They aren't.)
I just read a couple online reviews of the book and they all basically say what you've said. Its a "masterpiece" because he develops the characters and the setting so well and brings in all the varieties and situations one can experience in human existence; life, death, suffering, happiness, sadness, etc....
Whatever.
Man, harsh!
I've read his other "big" books, of mice and men, and the grapes of wrath back in high school ap english. We'll see if I pick one of those others ones Stephen mentions.
I actually think that Steinbeck is a better non-fiction writer than a fiction one; which might seem strange. But he was such a keen observer of the world around him, and his ability to describe people and places so vividly really lends itself to non-fiction.
Travels with Charley is my favorite book of his. If you want to get a feeling about what 1960 backroads America was like, this book does it.
I also really enjoyed A Russian Journal. He and Robert Capra, a famous war photographer, travel to Russia in 1946/7 and its just a fascinating snapshot of what life was like there right after the war.
Log From the Sea of Cortez is also great. He and his good friend the marine biologist Ed Ricketts rent a boat and go around the Gulf of Mexico documenting marine life in 1940.
America and American's is a collection of essays. There's a lot of overlap with Travels With Charley, but enough original that its worth a read.
He also has a memoir of his time as a war correspondent called Once There Was a War which is interesting.
He wrote a bit of wartime "propaganda", for lack of a better term, called Bombs Away: The Story of a Bomber Team. Its not a great book, but its really fascinating to read because you'll be plugging along with typical Steinbeck prose talking about what its like to go through training for a B-17 crew; and then your hit in the face with what is clearly copy pasted in by the US Army. I happen to have a first edition of this book as well, which is kinda cool.