D.D.
A lot of classic kids books are free downloads. For my 7 year old, I've downloaded Secret Garden, Black Beauty, the Jack London books allfor free. I've borrowed the Hardy Boys series from the library. (these are all books we read together, since they are above 2nd grade reading levels, but my son loves them).
Really, you can probably get about any kids' book from the library as an e-book.
For books to read on her own, see if you can borrow the Junie B Jones books from the library. Or the Judy Bloom "Fudge" series if she's an advanced reader (they are 3rd or 4th grade level).
My kindle is only a reader, it doesn't play games so I don't have any recommendations for games, just books.