'The Mortal Instruments: City of Bones' author Cassandra Clare discusses the upcoming movie

Clare said it was 'surreal' that the movie had finally come to fruition. The film based on Clare's book is scheduled for release on Aug. 21.

“The Mortal Instruments: City of Bones” – the latest young-adult-novel-made-into-movie that Hollywood is hoping will be "The Hunger Games" of summer 2013 – is hitting theaters Aug. 21. "City of Bones" is based on the first book of bestselling "The Mortal Instruments" trilogy by YA author Cassandra Clare.

“Bones” centers on a teenage girl living in New York City named Clary Fray (Lily Collins of “Mirror Mirror”), who discovers she has powers that enable her to fight supernatural creatures known as demons. Clary begins training to become a Shadowhunter, part-angels who fight the demons, along with other Shadowhunters like Jace (“Harry Potter and the Deathly Hallows: Part 1” actor Jamie Campbell Bower).

The film version of “City of Bones” also stars “Misfits” actor Robert Sheehan as Clary’s best friend Simon; “Game of Thrones” actress Lena Headey as Clary’s mother; “Gossip Girl” actor Kevin Zegers as Alec, a fellow Shadowhunter; and “The Tudors” actor Jonathan Rhys Meyers as the villain Valentine Morgenstern.

Clare told MTV the fact that the movie had actually come to life was “surreal.” Clare’s grandfather worked as a movie producer, so she’d seen projects fizzle.

“I always knew movies aren't really happening until they're actually filming, and I thought, ‘This will never really happen,’” she said.

The author said she watched the auditions for almost every actor, minus Collins, and told Publishers Weekly she especially supported the casting of Campbell-Bower. She also visited the set.

Clare said that when she saw the film for the first time, she got so caught up in the story that she occasionally forgot the movie was based on her own material.

“There are some really great character moments, where the actors just become the characters, and the way they play off each other is really fascinating,” she told the website Collider. “And there are some beautifully romantic moments. I was just swept up in the cinematic aspect of it, which was fun.”

An adaptation of the second book in the series, “City of Ashes,” is already set to begin filming this fall. The final book in "The Mortal Instruments" series, titled “City of Heavenly Fire,” is scheduled to be released next May. Meanwhile, Clare's “Infernal Devices” trilogy, which is based in the same universe as “The Mortal Instruments” and shares a few of the same characters, recently concluded, even as a new trilogy set in the same universe titled "The Dark Artifices" is scheduled for a 2015 release.