If you're selling an ebook on Amazon then yes they are going to do this hosting just like they do with the rest of their ebook lines. You'd have to talk with them about this and about getting signed onto their ebook service if you want to sell that kind of product through them (there will likely be a waiting period).
As for selling a digital book, honestly I'd expect it to come with visuals or be exceptionally long to be worth putting on a CD in todays market. Now of course if you sold it yourself you wouldn't email it, you'd have to setup a service whereby you host the file online either yourself or through a company and then people download the book from that.
Copy protection is also important to consider - Amazon mostly deal with this themselves if you go through them - if you go it alone you have to make a choice if you use it or not.
Another point to remember is formatting - what kind of screen can your product be viewed upon/is designed to be viewed upon.