Okay, that's not true, because I am an analytical type when it comes to my entertainment, but much less than some other things.
In short: very entertaining; successfully adapts the book in terms of streamlining and making emotions more present (Mark is a very peculiar brand of unreliable narrator, in that he says "I cried" and you don't really feel it on a gut level); surprisingly resists the urge to Hollywood it up until the end; could've done better on casting in terms of racial representation, but it could've been worse, too; whoever did the soundtrack was having a lot of fun.
As for the casting bits: Kapoor is Hindu in the book and is played by Chiwetel Ejiofor in the movie; he does have a line about his father being Hindu and his mother being Baptist in the movie, but when Irrfan Khan turned them down (h/t musesfool), well, it's nice they didn't go with a white guy, but it's not like there's only one Indian actor out there in the world, you know? With that casting, the only visibly Asian main characters were of East Asian ancestry. On a similar note, point for casting Rich Purnell (race not specified in book) with Donald Glover, and minus for not casting Mindy Park with an actress of Korean ancestry. (Point for making one of the guys in China a woman, as well.)
Finally, I don't know what Sean Bean and his non-American accent were doing in this movie. I am entirely willing to believe it was solely in the service of a particular meta joke that had the entire theater laughing uproariously, but I shamefully admit that I think it was worth it: the Rich Purnell maneuver is, as in the book, named the Elrond Project, and Sean Bean's character is the one to explain the reference to the Council of Elrond.
And now, some spoilers about the adaptation and ending:
The movie drops two major incidents, blowing up Pathfinder (which lets them keep Sojourner as a little mascot, which is cute) and the dust storm on the way to the pickup point. That was fine by me. Sadly, it also Hollywoods up the ending by having Mark do the Iron Man maneuver with a punctured glove to get closer to the Hermes (something he jokes about in the book), while Commander Lewis (Jessica Chastain) goes out to meet him. Yeah, it's pretty small in the scheme of things, but it's unfortunate because it's so obviously a dumb idea, you know?
The movie also doesn't end on Mark arriving on the Hermes; there's a montage after of the various characters as the next Mars mission launches and then Mark teaching a class to astronout recruits. I thought that was fine and fit the format better than the book's ending would've, but Chad thought it was cheesy, so YMMV.
I dipped into the fandom tag on AO3 and was depressed to find it was full of Watney/Beck (a.k.a. the power of two vaguely conventionally attractive white dudes—seriously, they have minimal interaction in the movie, and if you must break up canonical m/f pairings, Martinez is his best friend in the book), so I will take any gen recs from you all, but I can enthusiastically recommend the Interstitial series by Lanna Michaels, which is a book-style continuation (so far two short-ish pieces) that's perfectly in character and just terrific. Also, for the brilliant crack, Lanna also did a fusion with Jonathan Strange. And now the kids' morning TV is done so I will save the trailers until later.