I just got back from watching this - when I found my other half hadn't heard any spoilers it was an obvious choice what to watch. I'd read the book four years ago, so I remembered the story but not all the details.

We both had a great time and would heartily recommend it. Ryan Gosling filled out the character to a fuller extent then I remember from the book (I think Weir has gone on record admitting that character depth is his weak spot) and I can't fault the supporting cast. The score is excellent - lots of choral elements that suits the majesty of space. The visuals made me glad I was seeing it on the big screen.

They really speed-ran the early part of the book, but it would be a very long film if they added everything and I think it's a good adaptation of the book, and fairly faithful. They did include the setup (in a Chekhov's gun sense) to some things that weren't then mentioned; I wonder if that's as a nod to the book readers or if the rest is on the cutting room floor.

I hear they're going to do Artemis next, which I didn't read due to the abysmal reviews. I think it'll be worth watching as I expect they'll fix the flaws (which iirc was partly that it was just Watney again but in a unconvincing female role) but I won't read the book first.