Great spin-off that's well worth the price.
Pros:
+ Creepy Halloween-themed setting (Pyre Night).
+ Fun and quirky storyline with great narratives.
+ Awesome new vampire abilities.
+ UCG missions provide plenty of replayability.
Cons:
- Combat/deaths can be cheap and frustrating at times.
- Short campaign.
As you leap and/or fly around the city, searching for answers and Bloody Mary (the vampire puppet master), you'll be able to enjoy the life of a vampire yourself with a few new cool abilities, including turning into a swarm of bats. You may begin to think to yourself that maybe you DON'T want to be human again?
tl;dr: An interesting plot, a few new abilities, zombies, and vampires. What's not to love?