I'll begin by stating that I believe if you want a book, you should either buy it or borrow it from the library. That said, once I buy a book- either physical or e-version, I believe that specific copy is my property and I can do with it what I please (other than file sharing, of course). Thankfully publishers are starting to distribute without DRM (thank you Tor and Baen) and are beginning to stop treating us all like potential criminals.
The problem for me runs into storage, particularly with any books I purchase through Amazon. You can't expand the storage on a Kindle as you can with the Nook and some books are cheaper on Amazon than they are through B&N. Don't start with the 'cloud' business with me either... I don't live in the center of a city, I don't always have a reliable internet connection, and when the apocalypse comes (it is a joke, please laugh), that 'cloud' isn't always going to be accessible.
So, that leads me back to the evil DRM. I want to be able to bounce any purchase that I made among my e-readers (Nook HD+, Kindle Fire, and the iPad) and I can't... well, I couldn't... I can now, and so can you. I'm not a writer of tutorials... I have a short temper and I'm not a teacher, I don't have the patience- my many thanks and hats off to those who can teach and write amazing tutorials. I am going to leave you with this link from a great blog that will take you step by step through the process: