Si Vis Pacem, Para Bellum
Calibre is free on the computer. I'm not sure about a cellphone though.I LOVE Calibre! It's also one of the very few programs I have purchased an app for (the app, I think it was $1, will all you to transfer books from the Calibre program on your computer to your phone/kindle).
One cool thing about Calibre is that you can have more than just books in there, and you can also have separate libraries and easily switch between them. For example, I have a large collection of DND books. These are in a library all of their own. Some of them have maps in JPG format - and I can easily have these listed right in Calibre as if it was a book. I have two more libraries - one containing fiction and another non-fiction. I enjoy having them separated like that as it makes browsing and tagging easier. Tags are another fantastic tool - very easy to do. I really like the Dewey Decimal System and so I have tagged most of my non-fiction books like that. But what's cool is that you can give a book multiple tags, and it would show up under all of those. That's handy.
I also love how you can associate multiple file formats together as one listing - so if I have a book in pdf, ePub, and Mobi formats, I can easily combine them into one listing so that the book doesn't appear three times in my library. From that listing I can choose which one I want.
You might look into MusicBee if you have audiobooks or listen to podcasts. Make sure you select the Audiobook tab when you add the audiobooks - it will keep them separate from your music. Like Calibre, it will allow you to easily edit the Metadata to make it usable. You can import books as mp3's or m4b. For podcasts, you can have it only download the latest episode or ones you click on, or you can have it download every episode, and then you can tell it whether you want it to automatically delete older ones after a while or to keep them until you manually delete them. Very handy.
I keep all these on my computer hard drive, but I have two back up drives that every week or so (whenever I've got a bunch more to add) I copy everything over to them.
What I like about it is that you can open Dejavue files, ebook files, mobi files and PDF files. You can also convert each one of those files to one of the other files, such as mobi to PDF or visa versa