One observation from reading the posts in this thread is the number of times that Calibre is mentioned ...... no other personal library management system has been mentioned so far (I don't think).
We really do as readers of ebooks have a lot to thank Mr Koval for methinks!
Another observation is how important most of us think that copying our e libraries is and the steps we take to ensure the ebooks are 'secure' in the event of x/y happening.
It's also interesting to note that a great bulk of us seem to be reasonably aware of various software packages and work out how to integrate them with our personal needs.
Interesting stuff, eh!