I saw
The Martian today, with friends. It is excellent.
It's
very faithful to the book, albeit somewhat streamlined for time, as most adaptations must be. But perhaps more importantly, it's very smart. It's not dumbed-down at all for a mainstream audience. Plot developments are presented quickly and efficiently, with little exposition or explanation, and the audience is expected to have more than an 8th-grade understanding of math and science in order to keep up. In fact, the movie is even more "show, don't tell" than the book.
Spoilers follow for those who've read the book and wonder what has been changed…
The first nine months or so — up to the
Hermes' slingshot around Earth to head back to Mars — are taken almost straight from the book. After that is when things get streamlined. There is a "seven months later" jump to the preparations for the road trip to the Ares IV site, and Watney doesn't lose communications with NASA before the trip, so he doesn't lose NASA's help with overland navigation, so he never gets lost or rolls the rover like he does in the book. Altogether, the trip is presented as a rather uneventful montage. It's disappointing, but I can see why it was done.
Also, they changed one of the main running gags from "'70s sitcoms" to "disco music". If you've read the book, you know what I mean. It gives the movie a nifty soundtrack, though.
Anyhow, I hope the movie does well and maybe, possibly, perhaps inspires more interest in manned exploration of space.