I have not read Darren Shan’s novel saga, The Saga of Darren Shan, but given its enduring popularity, I imagine that it is a lot more narratively focused than the middling film adaptation, Cirque du Freak: The Vampire's Assistant. This film ticks a lot of boxes, with a lavish production and a varied and distinguished cast, but it is also overlong and underbaked, failing to fully capitalise on its rather promising premise.

The film’s protagonist is 16-year-old Darren (Chris Massoglia), who spends his time obsessing over spiders and hanging out with his best friend Steve (Josh Hutcherson), who is himself utterly besotted with vampires, and when the two are mysteriously invited along to a travelling freak show, Steve becomes convinced that the lead performer, Larten Crepsley (John C. Reilly), is a vampire that he’s read about in his books. From here, the two become embroiled in a war between vampires (the peaceful sort, led by Crepsley, who incapacitate their victims and then drink a small amount of their blood without turning them into vampires), and the dangerous vampaneze (who refuse to change their savage ways and continue to murder innocent humans), causing a huge rift in their friendship. The boys are dragged to opposite ends of the spectrum, with Darren joining Crepsley, while Steve flirts with the temptation of meting out his anger at his negligent, alcoholic mother on unsuspecting human victims alongside the vampaneze. Meanwhile, the mysterious and shady Mr. Tiny (Michael Cerveris) stands in the sidelines, egging on the war for what appears to be his own amusement.

With material like this, and the borderline-risqué treatment it’s given here, there’s the overwhelming feeling that the film would have benefitted from a “15” rating. Given Reilly’s strength in more adult pictures (such as Step Brothers and Walk Hard), his performance, although the film’s sure bright spot, feels muted and restrained, when it should be off-the-wall and probably quite offensive. Given how grotesque some of the creatures are - particularly Cormac Limbs (played by the lovely Jane Krakowski), a woman who can regenerate severed limbs, and also Alexander Ribs (Orlando Jones), a man missing the area of skin below his ribs – this is clearly a film that’s teetering on the adult precipice, but never quite goes far enough, presumably through fear of alienating its loyal fanbase of predominantly young readers.

Nevertheless, this isn’t so much a bad film as it is a sadly underwhelming one. It does, however, boast an excellent production design throughout; the gothic cinematography is rather inviting, and the visual effects (particularly those of the colourful spider, Madam Octa) are splendid, making the preamble of meeting the numerous freaks actually quite thrilling. The film’s chief problem, though, is that it just lingers around without direction for far too long; it takes roughly forty minutes for the film’s key dramatics to kick in, by which point the novelty of the impressive production has somewhat worn off.

What’s clear is that there is a great film waiting to be made within this overlong and ploddingly paced effort. One would think that a film based on three books would be densely-packed and brimming with energy and narrativity in every single one of its frames, but this film goes the other way, and it is the fault of scribes Paul Weitz, who also directed the film, and Brian Helgeland, who, having worked on L.A. Confidential, Mystic River, Man on Fire and The Bourne Supremacy, should probably know better.

Far from a mirthless effort, though, the film’s cast counts for a lot; Reilly is good fun as the lead, despite being in dire need of material with more bite (pardon the pun), and the two kids are decent enough for typical production-line Nickelodeon delegates, but it is the extensive array of cameos and bit-parts that keeps the film intermittently intriguing. Willem Dafoe, as Crepsley’s friend Gavner Purl, boasting a pencil-thin moustache and eerily resembling Vincent Price, takes some much-needed light relief after the torturous Antichrist, while Ken Watanabe makes a rather beguiling appearance as the big-headed Mr. Tall, and Salma Hayek, as the bearded lady Madame Truska, reliably fills the film’s cleavage quotient.

There are definite thrills to be had with The Vampire’s Assistant, largely thanks to some tasty gallows humour, but a talented roster like this unmistakably deserves better, more refined material that doesn’t strain over a 108-minute runtime. Through and through the film is aesthetically true, and the effects in particular are rather magnificent, but there’s the distinct impression that this is the laboured build-up to a sequel that should hopefully be a more rewarding experience, if, of course, this film can produce solid enough numbers to warrant that, which I am sure that it will.