Yes, I did make a Seinfeld reference in the title of this review. Does it have to do with Seinfeld? Not at all. But now that I've caught your attention, let me tell you about this amazing movie, and the amazing TV show that it's connected with.
Serenity is a full-length movie, and it continues on from the TV show, Firefly, which was unfortunately cancelled. Serenity is the name of the ship in Firefly, and it's also obviously the name of this movie. Serenity works as a stand-alone, but it works even better in relation to the TV show. I'd recommend watching Firefly first because Serenity takes place afterwards, but if you don't mind spoilers, I guess watch in whatever order you like. :P
This movie is awesome, as is the show. The characters are back, and they mean business. I loved getting to see a bit more of the crew of Serenity...especially since I definitely didn't get enough from the TV show. I don't think I'll ever get enough. I'll be re-watching this movie more than a few times. You can bet on that. I loved that through Serenity I got to hold on to Mal, Kaylee, Simon, Zoe, Wash, Summer, and Jayne a little while longer. You see Summer get into some crazy situations, and of course some of Mal's dealings that never seem to go the way that he planned...and you get to see some crazy altercations with the Alliance.
Now, you're probably wondering what this whole series is all about. Well, Firefly and Serenity take place in the future, Earth is now Earth-that-was and humans have expanded throughout a whole new universe. Mal's crew on Serenity are pretty much thieves, and they're not big fans of the Alliance (the governing body who unified the planets...but also pretty much control everyone). They smuggle, steal, and do pretty much everything to go against the Alliance. If you're new to Firefly and Serenity, as I've said, I recommend Firefly first, but I definitely recommend that you also get yourself a copy of Serenity to watch after you've finished the series because you'll definitely be wanting it! :D