History E book

This week as I was reading through my newsfeed I came across a history E book that has some great resources, links and ideas, it is also easily accessible. The downsides to this book is that some of the links aren't great (such as the quizzes) and there isn't a very concrete bibliography so it may not be useful for AP classes. Here is the Link: http://www.ushistory.org/us/   I think that E books are a great idea, espcially if you have students who have to take vacation. They will most likely be able to access their homework anywhere!