We Give Books
I've mentioned this site before, but it's worth revisiting as there are new books being added all the time. The books load in a Flash viewer which is fine for PCs but iPads don't like it, so try the browser Puffin or Rover, to see content. (Slow bandwidth might make them run sluggishly.) You will find a mix of fiction and non-fiction materials. A nice addition is an "Educator Resources" section that offers a range of activities and lesson plan ideas. Note: You will need to create a free account to read online.
"We Give Books" is a new digital initiative that enables anyone with access to the Internet to put books in the hands of children who don't have them, simply by reading online. (WBG was created by the Penguin Group and the Pearson Foundation.)