One of the goals of having technology is to allow personalized learning, and although we're getting closer with every app and website, we're not quite there (nor do I ever think we will be officially "there"). This app is a great push in that direction. Teachers can add students or give them a code and have them self-register, which is always easiest. Once students are in the app they can either browse books or read books from their library that have been assigned to them by their teacher.
At the end of each story students answer questions and teachers have the ability to monitor their classrooms. There is also a handy Text Complexity Equivalence chart that correlates common reading systems to help you figure out where a student should start.
The real beauty behind this system is that a teacher can assign the same book to different students at different reading levels and each student doesn't know which level the other student is at. It's worth checking out by downloading here! Plus, there is also an iPad app for teachers and students to use.