I have been struggling with this software for a week. Purchased a textbook and got through the introduction the first night. When i went back the next day to continue reading get error messages saying the book is registered to a different user. There is only one me, one passwork on two machines. Neither will open my book. Adobe says it is the textbook seller. Guess who the textbook seller says is to blame?! I'm tired of this. I will use Adobe at work where it is required. But never again.