This is one of the more odd vampire movies out there, thankfully a lot different than the TWILIGHT movies. The story is primarily about two high school friends, Darren and Steve. When they sneak off to see a freak show that has arrived in town, Darren becomes enamored with this really strange red spider, since he loves arachnids. And Steve recognizes one of the performers as a two hundred year old vampire named Larten Crepsley (John C. Reilly). Darren, out of character, steals the spider but not before he overhears his friend ask the vampire to transform him into one of the undead. The vampire tastes his blood and says it's no good and he'd make a bad vampire. Steve is angry.
The next day Darren takes the spider to school where it escapes and bites Steve, who lapses into a coma. In order to save him, Darren goes back to the circus for an antidote. But Crepsley agrees only if Darren agrees to become his assistant--which means he has to become a vampire. Darren dies and his family and friends think he's dead. Then, he begins working at this very odd place, the circus of freaks. There's a mangy flea-bitten werewolf and a guy with a really long head. There's also these small, golem-like creatures in robes which are a complete rip-off from the crushed down dead body dwarves in the PHANTASM films. It's way too similar for it to be a coincidence. They are even created by a scary looking dude named Mr Tiny (Michael Cerveris of FRINGE), who is a bit like The Tall Man. Things get complicated when Steve is transformed into an evil, murderous vampire and Darren has to fight his former best friend. Mr Tiny wants Darren on his side, a theme which I assume continues in the book series upon which this film is based.
Basically, THE VAMPIRE'S ASSISTANT it's an amalgamation of everything that's been done before. It's does for horror and vampires what the HARRY POTTER films do for fantasy. I recommend it much more for the visual effects than anything else.