I can see how you could not like it. Characterization is really thin, and that's usually a deal-breaker for me. I think it helped that I had been forewarned about it—and that I read much of it on a really long travel day involving multiple flights!

I've heard the film goes much more into the characterization, simply from its very nature: actors on screen. But Mark Watney was always on the line for me between "I love this guy" and "I could really hate this guy."