First of all, my overview of the preceding Underworld movies can be found here.
At the start of Underworld: Awakening the audience is told by Selene (Kate Beckinsale) about "the purge". Yes, humans finally discovered that there really were vampires and werewolves (aka lycans) and set about eradicating them. After telling the audience this information, Selene is then taken out of action and frozen. She ends up in a lab for many years. But the movie is called Underworld: Awakening so you may be able to guess that Selene doesn't stay frozen in the lab for the entire movie and when she gets out there are a few revelations.
If you enjoyed the first two Underworld movies then I can't think of any reason why you would dislike this one. It's more of the same and it's all done very well. Mans Marlind and Bjorn Stein share the directing duties and Len Wiseman (director of those first two movies) is one of the four people who helped to create the screenplay, which brings in a few new ideas and easily mixes them in with the familiar elements and style that fans of the movies have come to expect.
Beckinsale is the star of the show, once again all black leather and cat-like agility (is it getting hot in here or is it just me?) but there's a good supporting cast of players with the likes of Michael Ealy, Theo James, Kris Holden-Ried and Sandrine Holt doing a decent job. India Eisley is a very good young actress getting to play a very fun character and I was surprised to see Wes Bentley put in an uncredited cameo appearance. The most fun, however, comes from watching Stephen Rea and Charles Dance playing their parts. The two great actors appear to have a lot of fun while they play two very different characters.
The special effects are almost as good as they were in the second movie (which remains my favourite of the series so far) though there are definitely times when the CGI isn't quite up to the task, such as an otherwise enjoyable chase sequence involving Beckinsale, Eisley and Theo James trying to drive away from relentless lycans.
Overall, however, this is a bloody good time. The action feels as if it is non-stop, the visuals are cool, there is a nice helping of gore and bloodshed and the development of the characters this time around takes one or two interesting turns. Okay, it also feels very lightweight (thanks to the streamlined storyline and the runtime clocking in at about 85 minutes, despite the IMDb listing putting it at 88 mins, including the opening recap for newcomers) but it's blockbuster fun and that's all it wants to be. Mission accomplished.