I wrote a piece about the app on my homeschool blog called "A Fabulous Reading Find". Click the title to visit the article and you will see my thoughts on the app.
I can sum it up by saying that I think it is a great buy. Grandparents or Aunts and Uncles might consider giving this $50 a year subscription to a family of young ones to inspire reading and lots of fun. We love that it is al the apple I-pad but also the Kindles.
The twins do not have their own kindles but can often be found using mom's or other siblings so they can sit down and read a "book, a reading rainbow book!"