The free app , offering more than 150 multimedia books for kids--the target audience is age 3 to 9--along with Burton-hosted videos depicting trips to submarines, museums, and other interesting locations.

When you open the app, it asks you to enter a name, age, and gender, then to select three favorite topics from a list of 9. My 3-year-old son, Tobias, assisted me in this task, choosing "Things That Go," "Space & Beyond," and "Pirates" as his favorites.

Once that data is entered, the app offers a series of subscription options--becoming a sort of Netflix for kids' books in the process. You can choose not to pay anything for the app, but that will limit you to just one book from the app library, along with access to the videos. The other options? A $10-a-month subscription, paid through iTunes, that automatically renews each month--or a $30 subscription good for six months. (Note that the app isn't produced by non-profit PBS; rather, it was created by , a private company co-owned by Burton.)

If you do subscribe, you have access to the entirety of the Reading Rainbow library. You can find books on a series of floating islands: One is focused on "action adventures," another is named the "Genius Academy," a third is focused on animals, and the last on friends and family.

Touch one of the islands, and you'll see a series of book covers--the first few of which are recommended based on the interests indicated when you first open the app. Touch the book and you're given the option of downloading it to the app.