This site has an interactive library full of different level texts and reading resources to build reading skills. In addition to hundreds of books to explore, there are fun videos adventures, and virtual field trips. There is also an app available for download for iPhone, iPad, Kindle Fire, or Android. It is not free to subscribe. Prices run $4.99 for a month-to-month subscription or $34.99 for an annual subscription. A free trial is offered.