Fangs for the memories.

First off, let's get one thing straight. It is practically a rule in Hollywood that the sequel of a movie is supposed to suck. No pun intended. Anyway, there are rare instances (Terminator 2) where the sequel far succeeds the original. This is one of those exceptions.
Underworld:Evolution takes off from the first movie and it is helpful (but not manditory) to have seen the first movie. There are flashback sequences (from the first film) interladen in the film that give you enough backstory to progress the movie along so you do not get lost. It's helpful for those such as myself whose memory is less than perfect. And they are placed where they should be, unlike other sequels where the flashbacks should not have been in the movie to begin with. Another thing is that this movie has more of a flow to it, which the first film was lacking in various places. This film never became stagnant, which in my book is a good thing. It kept progressing at the same speed (which the first one did not) and had a very satisfying ending.
The best way to describe it is that it is a very visual movie. Despite that it is dark (literally) throughout most of the movie, it is also very captivating. Yes there is plenty of violence, blood, and some nudity; but how should any of this be a surprise. Overall, I would give this film four out of five stars. Considering the fact that there are a lot of disappointing vampire films out there, this one is not one of them.