Monsters are the worst kind of party crashers. They show up uninvited, they completely trash the venue, and they spend much of their time brutalizing the other attendees. They know how to ruin a good time, and the characters from Book of Monsters could certainly attest to this.

Written by Paul Butler and directed by Stewart Sparke, Book of Monsters is a British comedic creature-feature that follows Sophie (Lyndsey Craine) who, with help of her friends, must find a way to defeat the bloodthirsty monsters that crashed her 18th birthday. This proves to be a difficult task, but Sophie proves herself to be a worthy adversary in this delightfully zany, albeit flawed, old school monster movie.

Before we can delve into monster-mayhem, we need a group of characters to face off against them. Thankfully, Book of Monsters delivers in the casting department. As the film’s protagonist, Lyndsey Craine gracefully balances strength and vulnerability in an impressive performance, making Sophie a worthy heroine. Equally as impressive are Sophie’s two best friends, sassy-girl with a heart of gold Mona (Michaela Longden) and goth-chick Beth (Lizzie Aaryn-Stanton). The trio has great chemistry together: they’re funny, charismatic, and likable, and as a result, the audience cares about their survival.

Once the trio of heroines discovers that five monsters will be sent wreak mayhem over the course of the night, the film keeps the story moving at a fast clip and the audience is introduced to a quintet of memorable monsters. The creature design on display here is top notch, and the fact that all of them are brought to life with practical effects makes their appearance even more impressive. Their appearances range from grotesque to endearingly wacky, and they bring with them a whole host of entertainingly madcap kills as they slaughter their way through partygoers. It makes for some amusingly gory set pieces.

But for all of its strengths, Book of Monsters isn’t perfect. Most notably, the film suffers from some shoddy editing choices. The more action-oriented scenes are cut within an inch of their lives, and they are so choppy that it can be somewhat difficult for the viewer to discern what exactly is happening. It does not help that the audio cracks and pops with every cut rather than smoothly flowing from one shot to the next, causing every edit to feel jarring and disjointed. That’s not to say that the film is technically inept: the cinematography here is quite competent and the lighting is effectively atmospheric. But further editing and audio passes on the more frenetic sequences could have greatly improved their success within the film.

Putting its technical shortcomings aside, Book of Monsters is a fun monster mash that is elevated by good performances and memorable creature designs. The cast and the filmmakers effectively communicate their passion and personal enjoyment for the project, and their enthusiasm for the material is infectious for the viewer.