They say it's in the running to be the next big thing since Twilight but if you're going to see The Mortal Instruments and haven't read Cassandra Clare's book yet, then there are a few things you'll need to know in order to understand what's going on.

1. What's the story?
The Mortal Instruments tells the tale of a young woman by the name of Clary Fray. She assumes that she's just your average Brooklyn gal until she starts seeing a strange blonde lad that nobody else can spot, and her mammy is kidnapped by some seriously strange looking dudes, who just so happen to keep a demon handy. Thing is, Clary's a shadowhunter, a half-human half-angel warrior destined to protect the world from evil.

2. Who are these people taking over the cinema screen?
Well, you've got your heroine, Clary (played by Lily Collins) her best friend Simon (our own Robert Sheehan), and secretive sassy Shadowhunter Jace (Jamie Campbell Bower), who basically introduces her to the Shadow World. She's on a mission to find her mother, Jocelyn Fray (Lena Heady), who has been kidnapped by one pretty twisted Shadowhunter, Valentine (Jonathan Rhys Meyers). Jace comes along for the ride and brings with him his best pal and adoptive brother Alec (Kevin Zegers) and his equally sassy sister Isabel (Jemima West). The pair are pretty savvy Shadowhunters, but that doesn't need they won't need to call on Brooklyn's High Warlock Magnus Bane (Godfrey Gao) from time to time. And if they ever find themselves running low on knowledge, they can always turn to Hodge (Jarden Harris), the fountain of knowledge who keeps watch over The Institute, New York's Shadowhunter HQ. Oh and then there's the mysterious Luke (Aidan Turner), Jocelyn's best bud and the man Clary considers to be the closest thing she has to a father. If only she knew what he was really like...

3. Why are they talking in code and covered in tattoos?
You're going to see plenty of ink and hear an awful lot of new lingo in this movie, so getting up to speed before you go is key to enjoyment.

First off, those markings are known as runes, and are special markings used by Shadowhunters to give them special powers. They use a special weapon called a steale to carve them into their skin, giving them the ability to do all manner of things, from seeing past glamours (which hide the Shadow World from mundanes - we'll get to that one in a minute), to healing wounds, and even using angelic power to get rid of those pesky demons.

Shadowhunter v Mundane: There's one big distinction to be made between Shadowhunters and normal humans. Shadowhunters are human, yes, but they've also got angelic blood coursing through their veins. The demon hunting race is over 1000 years old, and all its members are dedicated to protecting mundanes aka normal humans without angelic blood, from being terrorised and killed by demons.

Downworlder v Demon: You'll find werewolves, vampires and demons in this here movie, but believe it or not they're not tarred with the same brush. Werewolves, vampires, warlocks and fairies are classed as Downworlders, beings who aren't human but not exactly demonic either. Demons, however, are beings of pure evil who travel from dimension to dimension leaving death and destruction in their wake.

4. Are we looking at another Team Edward/ Team Jacob situation?
Most definitely. Clary's instantly attracted to Jace, the boy she can see when nobody else can, but that doesn't stop her pal Simon pining after her. You'll most likely find yourself torn between the two, as these boys prove they're both oddly quirky charmers. We won't tell you who we'd fall for, because that would just be cheating.

5. Will there be another movie after this one?
Fans of the book series will know that there are actually six installments begging to be adapted for the big screen. Well, five at this point in time actually because the sixth book isn't due for release until next year. Book 2, City of Ashes, has already been given the green light and the gang are due to start shooting in Toronto in September. We do hope you've been paying attention, because it looks as though Clary and co are most definitely here to stay.

The Mortal Instruments: City of Bones hits Irish cinemas on August 21st.