The best-seller list. Reading them. But bianna golodryga, what is it? Flying off store shelves. A lot have read these books ale a series of six "mortal instruments" replaced "hunger games" with... See More
The best-seller list. Reading them. But bianna golodryga, what is it? Flying off store shelves. A lot have read these books ale a series of six "mortal instruments" replaced "hunger games" with legions of fans hungry for more of the supernatural tween thrillers and spoke to cassandra clare about her fever for the novel. This morning the hottest selling tween thriller on shelves is also in theaters. You know the mundane. The mundane. Someone from the human world. Reporter: "City of bones" part one of the six-part series recently topped "the hunger games" series on "the new york times'" best-seller's list number one for nine weeks straight and it's now a major motion picture. It stars jonathan reese meyers and lily collins as the lead role of clary fray, the seemingly ordinary teen who battles extraordinary villains from demons to vampires and werewolves. What do you think about her? She's different. She's going to get us all killed. Reporter: We sat down with the author of the series. Take us into your brain. Where did the idea come from. I was fascinated by mythology and demons and angels and wove those things together and also the granddaughter of a producer of horror movies so I have an imagination that always goes to those places. Reporter: Her grandfather, max rosenberg behind more than 50 flips including "tales from the crypt" and "the land that time forgot." Your books are a hit especially with teens and the twooeps. Were you worried at all this might be a bit too dark, too scary for that age group? I wasn't because I think children are fascinated by fear, by monsters by the teaming of monsters and darkness and so i think that to give them the darkness in a safe way to play around with it is actually perfect for that younger age group. I'd rather die than darn. Reporter: Other teen thriller books helped pave the way. Bella from the "twilight" series and katniss from "the hunger games." How important is that to the new generation riding the books to have female heroes. I think very important. We see people of all ages and gepdzers embracing these stories about strong women and I think that it proves that that's something that we want to see. Reporter: And when it comes to strong women it's not just about the written characters, but the writers themselves. Which raises the question, is there any rivalry? Success for one is success for all of us. The better we do as a group the better for children's publishing and more respect for the kind of writing we do. It's about more than us. inspiration for other female authors and the book "city of bones" in stores now. The movie is in theaters now and its sequel is already in the
This transcript has been automatically generated and may not be 100% accurate.