My Kindle Fire Doesn't Like Books!!

Last Chrismas I got a Kindle Fire, and I realized my Kindle wont read the books i purchased the right way. Lets say I bookmark the page I am reading. I turn off the kindle and go to watch TV. When i come back,turn on my Kindle, and go to the book, the book mark will go to a different page! And it seems that the letter forrmation and size are different each time. Its like the producers focused more on the games you can play than the books you can read on the kindle.

Picture From Here