Chel, I read Up the Down Staircase ages ago. A lot of resonance when I began teaching.
The Martian movie was, I think, generally faithful to the book. Obviously, they had to leave a fair bit out. And I did feel that there was a difference in how some of the characters related. The author did a lot of research and the knowledge blended well with the fiction, except the movie had something completely unbelievable near the end.