Good critics discuss the entertainment value of a book, but they also look deeper into the elements of literature. Be a critic.
I don't think this book is in any way "less than important." Steinbeck loved the Mexican culture, had just experienced the birth of his son, and drew on an old story he'd heard while traveling for inspiration. The story might be called entertainment by some, but I have never read a novel (barring fluff books for beach reading) with the intent to be entertained. Educated? Yes. To be made more aware? Definitely, but not purely for entertainment.
Steinbeck embraced the fact that everyone dreams, and although some people realize their dreams, whereas others never come close; there are those who lose everything from their pursuit. This story is a perfect example of "be careful what you wish for." I wouldn't change a thing.
