I regularly stalk Amazon.com (my favorite web site ever) for free books. Here are some I have found. All of these books have at least 4/5 star ratings on Amazon. I really do not like to waste my time; therefore, I'd would never read or recommend a book that has poor reviews!
Also, keep in mind, the prices of these books may change at any time. There were free when I found them.
Kids and Teen Books