Kindle and Calibre
Calibre might not be a pretty app, but for manging a Kindle library on and outside of the Kindle device, nothing else comes close. I buy all my books, but the first thing I do is to strip the copy protection from them. Thanks to Calibre’s plugin architecture this is a simple process using the DeDRM plugin. Many moons ago I had a sizeable library of books on the Palm handheld that I lost when the platform went belly-up.
Now I just want my books to be available to me independently of who is supplying the underlying technology. I don’t expect Amazon to fold anytime soon, but to be able to read the books I have bought from them on their platform or outside of it ois important to me.