It's good they all get their happy ending. Pretty ok, adventure friendship, it's lightweight and smooth sailing despite the deep conspiracy and drama as background setting. A little comedic, well basically don't take it too seriously it's enjoyable.
The manga is just as great as the anime! I feel like many stories try to do something interesting with the sci-fi genre, but it's either one of these masterpieces that are hard to get into, or unambitious (sometimes too ambitious) stories that turn mediocre at some point. This is neither it's really entertaining from the beginning till the end.