This book was the movie on steroids! this is a good thing, a great thing. it means that the movie stayed incredibly true to the book :) they key difference is how it all ends. 

I adored Weir's writing style, and the nerd in me rejoiced at Watney's antics even more than I did with the film. Of course, having seen the film first, I kept picturing Matt Damon. Mental Fan-casting ruined. Alas, it was totally wicked :) Suffice it to say that I get why they picked Matt Damon, the character felt written for him.