In squeezing the first three books from Darren Shan's young adult vampire series into one film, writer-director Paul Weitz (2006's "American Dreamz") and co-writer Brian Helgeland (2009's "The Taking of Pelham 1 2 3") have done a respectable—if not consistently airtight—job with "Cirque du Freak: The Vampire's Assistant." As a setup for further adventures, it serves as a promising first chapter, an involving if certainly morbid tale that has been misrepresented in its marketing campaign as a comedy when, in fact, it takes itself more seriously than not. The pacing is off at times, going too fast and then meandering, with certain character relationships and motivations underdeveloped and rushed, but the expectation is that this can all be worked out in later sequels. The scary proposition is that if it is not successful enough to get a second part, it will pretty much deem this one worthless on its own (sort of like what happened to 2007's wonderful-but-now-obsolete "The Golden Compass").

16-year-old Darren Shan (Chris Massoglia) is a straight-A student tired of always trying to live up to the lofty expectations of his parents (Don McManus, Colleen Camp). Best friend Steve (Josh Hutcherson) is a rebellious type, a bad boy with few future prospects whom Darren, oddly enough, kind of looks up to. When the two of them are mysteriously invited to a freak show at an abandoned theatre in town, all is fun until Steve recognizes Larten Crepsley (John C. Reilly) as a vampire he has read about in one of his books on the supernatural. After hours, Steve approaches Crepsley and pleads for him to make him a vampire—a shocking admission that Darren spies upon as he hides in Crepsley's closet. Steve is turned down, instead going into a coma after receiving a lethal bite from Crepsley's pet spider. To save his friend by way of an antidote, Darren makes the ultimate sacrifice to become a half-vampire, forced to fake his death and abandon his life and family as he joins the rest of the freaks on the cirque campgrounds. Meanwhile, the fight between regular vamps—those that drink human blood but do not kill their victims—and the sinister vampanese—those that literally go for the jugular—is about to heat up, with Steve approached by Crepsley's adversaries Mr. Tiny (Michael Cerveris) and vampanese Murlaugh (Ray Stevenson) with a soul-selling offer he can't refuse.

"Cirque du Freak: The Vampire's Assistant" opens terrifically with an animated opening titles sequence to make Saul Bass proud. From there, director Paul Weitz briefly flirts with the teenage satire stylings of Alexander Payne and 1999's "Election" before settling into more conventional storytelling mode. Even for a PG-13 movie (and one that has precious little actual onscreen bloodsucking), the film is surprisingly subversive, not shying away from the parallels found between the allure of vampirism, the burgeoning of adolescent sexuality, and the longing for carnal gratification. Whereas Darren did not want to become one of the eternal undead and resists blood, clinging to a humanity that he's afraid he'll lose if he takes that next step, Steve is unhappy in his life (his father's gone, his mom's an alcoholic) and is seduced by the power and control he believes go hand-in-hand with becoming a vamp. That Steve loves Darren and feels abandoned and betrayed when Darren leaves him and joins Crepsley only adds fuel to the fire. The reason behind Darren's decision is beside the point for Steve, antagonism growing in their time spent apart.

The jury's still out on the casting choice of newcomer Chris Massoglia as Darren Shan. He isn't bad, but the viewer gets the sense that he could greatly improve with more experience. It doesn't help that Josh Hutcherson (2008's "Journey to the Center of the Earth"), a veteran actor at just seventeen, is so much more appealing than him. When Massoglia is front and center, you find yourself wishing it was Hutcherson in the lead role, or at least someone who could come close to matching him in screen presence. As Steve, Hutcherson radiates the poignancy of a teenage boy giving up on himself and the dastardly thrill he experiences after he has handed himself over to the dark side. He struggles with some of the dopier lines of dialogue—"You have your destiny, and I have mine," he tells Darren at the end—but that is the fault of the writers, not the actor. As Crepsley, John C. Reilly (2008's "Step Brothers") disappears into his role, playing things on an appropriate lower key than his recent comedic work indicated he might.

The supporting ensemble is a memorable bunch, though with so many of them and so little time they are not always developed or paid enough care to. Salma Hayek (2007's "Across the Universe") makes the most of her brief screen time as Madama Truska, Crepsley's alternately stunning/bearded girlfriend, though not enough is learned about her for the character to be fully realized just yet. Jessica Carlson (2008's "The Life Before Her Eyes") is a sweet-faced eye-catcher as Rebecca, a girl Darren befriends within the community of freaks. Michael Cerveris (2001's "The Mexican") is creepy and sleazy as Mr. Tiny, who arguably orchestrates the entire plot and tells Steve at one point, "I love your DNA." Other actors, like Patrick Fugit (2004's "Saved!"), Jane Krakowski (2008's "Kit Kittredge: An American Girl") and Orlando Jones (2007's "Primeval") as other freaks Darren meets along the way, have either seen the majority of their work hit the cutting room floor or have been promised expanded roles in a continuation.

If "Cirque du Freak: The Vampire's Assistant" doesn't wholly capture Darren's sacrifices to himself, his friends and his family with the emotion hoped for—a scene, though, where he climbs into his parents' bed and tells them how much they mean to him is touching because he, and the audience, knows it may be the last time he sees them—the film maintains an edginess that knocks it away from strict family fare. Classy cinematography by J. Michael Muro (2008's "Traitor") is drenched in fog and shadows and, as Madame Truska warns against, "foreboding," while the music score by Stephen Trask (2008's "Sex Drive") knows how to pump up the energy with a booming orchestration. Allowing certain moments time to breathe while altogether tightening the screws of the narrative could have only helped, but when "Cirque du Freak: The Vampire's Assistant" works, it really works. There is an undoubted vision behind the cameras, one that is bound to only crystallize if the powers-that-be give this potential new franchise the nurturing it deserves.