I read this one back in high school, and often cite it as one of my favorite sci-fi books. I think it will keep that status, if mainly beause it was like nothing I had read up to that point. Interestingly, the technology in the book isn't very dated, but the characterization and limited plot do feel a bit dusty. (There is a paragraph explaining how boobs work in zero G, as if female astronauts wouldn't wear bras, just as a for-instance.) And yet, it's still a fun book–in a way it reminded me this time of the straightforwardness of Old Man's War by Scalzi.
It's still a fun, quick read, if one likes first-contact stories. I remember not loving the sequels much, and probably won't go on to them, but it was fun to revisit this one.