Protect a shopping cart and url

I have a pdf book which I've converted to a flip book using epagecreator. It produces both a Flash version and HTML5 version which can be read on a tablet or phone. The system works extremely well and the end result is attractive. I want to sell access to the book which ends up on my site as an html index file that accesses the rest of the data that is spread out in a variety of folders on the site. I'd like it to be purchasable using Paypal.
It is not downloadable but accessed online only. I want to protect the process in some way where all the urls are hidden and where the purchasers can't pass on their links to the book.
I am looking for suggestions as to the best way to do this and am open to all possibilities.
I normally post jobs on vWorker where I have a long history but as they have now been taken over by Freelancer and have not migrated my details correctly, I'm coming over here to try.