I'm on R.J.'s team and for a limited time only he has one of the Wurthington Diary adventures, Kindle version, for 99 cents.  This is an awesome book for kids and adults that like adventure.  Reynold Jay did a wonderful job of mixing in true history which makes the book all that much better.  Duy Truong is an awesome illustrator and the book is filled with wonderful images.  Here is the link for the book, remember it is only 99 cents for a limited time:  Buffalo Bill and the Pony Express (Wurthington Diary #6)  Don't worry that it is the 6th because it does stand alone.  At this special price though you can get a taste of what the series is like.