How to download emailed e-books?

My friend emailed me links to 3 e-books that I have to download somehow. I would like to either read them on my Mac or on my iPhone but I'm not sure how to put them there. If I download them from the email, they show up in a locked document. Any help would be appreciated!

If the books are in copyright, you have stolen merchandise. They probably have viruses. I would not download them.