The book I chose that was made into a movie is called The City of Bones. It talks of a girl, Clary Fray, who one day discovers she is a Shadowhunter-part of a breed of half-angel warriors dedicating their life to fighting demons. Her mother is attacked and kidnapped by the evil Valentine Morgenstern, and as she tries to find her mother again she meets new people, including Jace Wayland/Lightwood/Morgenstern/Herondale. She fights vampires, discovers her mom's best friend Luke is a werewolf, and meets a warlock named Magnus Bane. Not only is she pulled into this giant wave of horror and awe, her best friend Simon, who is a mundane (mortal), is unforturnately pulled in with her as well. 

The movie is, unforturnately, not very close to the books. However, it has managed to capture the main ideas and several very important scenes. The idea of family and love entwined with the adventures are very important. Jace, whose father was killed when he was 10, hides his real self under a cocky facade and does not let anyone crack it until clary comes along. His adoptive family cares for him (Isabelle and Alec Lightwood), and it has gotten to the point Alec has a crush on Jace (they're both guys). When Clary arrives, she breaks it all by introducing both herself and Simon to their world. Isabelle, who had never found any boy worth her intrest for long, starts to befriend Simon. Alec is initially hostile to Clary as it is clear from the start that Jace likes her. She discovers Alec's secret (that he is gay) and their relationship worsens, but near the end of the book some tension alleviates as they fight in battle together and they become friendly.