Basic and Advanced US History e-textbook

I am getting to the point where I hate to use the word e-textbook as it implies a paper version online (which is what the following two books are).  A teacher (or an e-textbook provider) should supplement it with many interactives (which is like I our Patterns of Interaction world history books).  At any rate if you need to save money on books or want to supplement them, I have a few listed on the side of this blog.  Here is a basic US text and here is a more advanced one from C-12.