This is another classic that was familiar as I started to read it; I think I'd tried twice before. Knowing more about the author helped me push through a lot, and it was worth getting through, but of course I have complaints.
The two timelines is one thing I"m doing with my novel (I think that is why this was recommended to me by a writing partner). Because we have the later timeline and we know <spoiler alert> he's going to get kicked out of his country as a traitor, the mystery of the younger timeline becomes: how? Unfortunately, it seems we're shown that he is different from toddlerhood on: not wanting to share. In retrospect after finishing, this might be that everyone is like this--the effort required to turn all humans into communal, sharing people--but while reading it felt like he was just different. So then it seems obvious how he will get kicked out as a traitor.
In the later timeline, the fun was seeing an individualist society through the eyes of someone raised communally. It is also suprising to find that he doesn't like it, since his younger self seems destined for that path, and the tension in the later timeline comes down to: will he make it home again? It is a relief, then, when he's back on the ship, but it is ultimately unresolved. He was kicked out of his society. This ambiguity didn't quite work for me.
I did enjoy the balance of the cultures: how neither is all good or all bad. That is something else I'm striving for in my work, too.