E-book Application- Activation code generation ways

I intend to make and sell e-books across the mobile devices. And of recent I came across ‘’open heavens 2014’’ in Google play and I downloaded it on my hand set and after the installation it asked for ‘’Please enter your PIN to activate the app’’ you can visit www………… to purchase an activation code.
I see this as a very good way of controlling the piracy, coping and duplicating the e-book
Is there any of my seniors in this forum that knows how to go about this type of e-book protection? Generating the pin code to protect the application? Please advise