Wow! This floored me. As I was reading I didn’t quite see where it was going. I knew that people generally categorize this as "philosophical" sci-fi, and I just wasn't really getting that. In retrospect, I think that's because the prose is so suited to the characters and the story. The ending was so moving, and fully recontextualized the novel to help me see how well structured it is. I can't wait to reread this, I feel like I'll enjoy it even more.