I love how this book is written. The odd chapters (1, 3, 5, etc.) are short, 3 or 4 pages, and provide a general description of the Great Depression, the Dust Bowl, and the challenges the homeless migrant families faced as they headed west. These chapters put the story in context and usually foreshadow the even chapters. Then, the even chapters (2, 4, 6, etc.) are a telling of how one family in particular (the Joads) respond to these challenges.
The book's ending is quite abrupt and, at first glance, anti-climactic, which is something I'm learning to expect and appreciate when it comes to Steinbeck novels. I won't spoil the it for you, but what I got out of this book, especially the ending, is that human dignity is most effectively obtained and imparted while debasing oneself in the service of another.
If you're gonna read only one John Steinbeck novel in your life, read East of Eden. If you're gonna read two, try The Grapes of Wrath.