The book is an 8+ hour investment, and by and large it gives good return on that investment the whole way through. The movie is a 3 hour investment, and it does the same. Both mediums gave me the experience of laughing my way through a deadly experience, and I highly recommend either one.
I recommend the book to everyone who:
- Wants to get the feel of the science behind the decisions the character makes
- Wants the feeling of an alien disaster to fully permeate their imaginations
- Wants to enter into Mark Watney's psyche
I recommend the movie to everyone who:
- Wants to share the laughter and fears with others as part of the experience
- Thrills to see human emotion as opposed to visualizing it
- Would rather block off 3 hours for the experience than catch as catch can with a book for 8 hours spread over however many days
Both gave me the same laughter, fear, and tears, but they did it in different ways and on different levels. To be sure, the movie added some preachy moralizing at the end that wasn't in the book, but I can live with that. The book is probably the better personal experience, if you have the time to invest, but there's something special about the shared experience of the movie.
As for books allowing you to really get into the character's head, I'm not so sure that's correct. The movie simply had to cut 6 hours of the experience. Many actions and events didn't make it into the movie, but virtually all the feelings did. Over and over again, I saw Mark Watney react emotionally to some event, and felt as much a part of it as when I was reading. A thing explained deeply in the book was a fleeting glance in the movie, but I found both powerfully fun.
Both are good for 4.5 out of 5.