Damn good movie, but felt some scenes were gone such as Beck and Johanssen's romance, why Mark stopped communicating with NASA during the journey to the Ares IV MAV. But seeing his face on enjoying Cmdr Lewi's least DISCO music was worth it. Reminds me of BangkokBoi.
The eBook (OK, I might want to buy the real book)
Fills in much of the 'missing' stuff from the movie. But no Iron Man. The ending was well, not so dramatic compared to the movie.
Watch the movie then read the book and not the other way round. Both complements each other unless the soon to be launched 'Extended Cut' version says otherwise.
The Martian's 'ARES III' Crew from Blastr