Level It Books is a very handy little iOS app. It uses the camera of your iPad or iPhone to scan the ISBN (bar code) of a book and give you the Reading Level of the book.
Scanning the bar code gives you the Lexile, Guiding Reading, Grade Level Equivalent, or DRA levels for the book you've chosen.
Scan Bar Code to Find a Book
Scanning a book's ISBN/bar code makes it super easy to locate the book's Reading Level.
Manually Searching for a Book
If your book doesn't have a bar code or your device doesn't have a camera, you can look up the book by typing in the book's information. If the book is in the Level It database, it will pull it up.
The app also allows you to create a digital roster of your class. This makes it very easy to track reading levels over the course of the year and also to loan out books from your class library.