Let's just get this out of the way - the movie is not the book. Now that we've established that truism for most book-to-movie adaptations, let's move on.
Just to give a little background on my mindset before I viewed this movie, I am not a Kerouac fan. Reading Kerouac as a black woman, is like repeatedly sticking a fork in my eye in some parts. It's painful to read the misogyny and the romanticism of picking cotton (When I read he thought he could make it his "life's work," I almost threw the book out of the window). But, I continued and actually understood his mindset by the end of the book. However, I really never wanted to be in his head again. It was a scary place.
So, as you could probably tell, I had my reservations about the movie. However, the cast won me over. When you have Amy Adams, Viggo Mortensen, Steve Buscemi, Kristen Stewart, Garrett Hedlund, Sam Riley, and Kirsten Dunst all in one movie, you can practically guarantee some fine performances and I wasn't disappointed at all. In fact, I'm a huge Kristen Stewart fan, in particular, and she blew me away, per usual.
On the Road is a story about a search for meaning in life - the "It." These young people were driven by their personal searches for God, their fathers (and in some ways their mothers), and a place to call home. They found all of those things in each other. Particularly, Sal Paradise (Jack Kerouac) found those things in Dean Moriarty (Neal Cassady) and vice versa. They hurt people along the way and made horrible life choices. But, they lived put loud and inspired others to do the same. This movie did an amazing job of showing the joy and pain in this journey that Sal took.
So, if you like road movies about self-discovery and you want to see America roll in front of your eyes in all of its beauty and harshness, then you will enjoy this movie. It's not the book. It's its own thing. One thing I wish Walter Salles, the director, and the screen writer, Jose Rivera, would've done differently is show how interconnected Sal/Jack started to feel with the world. He started to see his friends in people of all different races and backgrounds. He started to see himself in everyone. "Life is the road and all roads lead to the world." He became a world citizen because of his travels and I think that would've been important to emphasize somehow. It's the same thing that Malcom X discovered before he was killed and Martin Luther King, Jr, knew before he was murdered. I'm not comparing Jack Kerouac to these men. I'm just saying that they all became global thinkers.