Scholastic Storia allows books to be download (free & $).
Books can also be found by Accelerated Reading Level. Some stories provide questions and activities during reading. App allows children to read stories independently and get help with words as they read.
Both app's allow you to create goals with your child and monitors their accomplishments.
Great app to scan books on the spot to check Accelerated Reading Level. Also allows you keep a library of all books scanned and level them in order