There are currently six books in the Gallagher Girls series. The sixth book, United We Spy, was published on September 5, 2013. Ally Carter has said on multiple occasions that it is most likely the last in the series. Right now it looks like there isn't going to be a movie, but that could change. The series is suitable for teens ages 12+. There is no inappropriate language or sexually explicit scenes, though occasionally there is a bit of suggestiveness. Darker themes are introduced later in the series, especially in the fifth book (Out of Sight, Out of Time), but the only thing you really have to worry about is the state of your heart after you inevitably fall in love with one Zachary Goode.