Hi,
Yes that's possible if you know PHP. First, change the checkout workflow so that you have it in two steps. On the first step, you need to have only the cart view.
Then, you can go in the menu Display->Views and edit the file cart of the view checkout. You will have to add some code in that view to check the latest product added to the cart and if it's an ebook display that intermediate code instead of the cart. You can use the HTML add to cart link of the real books in order to have a link the user can click on to add it with only one click to the cart.