We're reading this one for my at-work bookclub, looking forward to it. We did the Martian back when and people enjoyed it. Although easy reading it has enough depth to spark a good discussion.
It's an interesting choice for a book club. Due to the way the narrative progresses (you start with an amnesiac protagonist and gradually reveal backstory via memories) discussions could get tricky/problematic if anyone is reading ahead faster than the rest. Obviously all books have some risk of that but PHM is more challenging than most in my opinion.
