Managing big e-book libraries: How do you do it?

I jumped on the e-book wagon when it first appeared on the mobile horizon, perhaps a decade ago. I remember discovering the benefits of reading books on my Palm XV, purchased from the Peanut Press. I found I read far more than I ever did with paper books because I always had my Palm with me, followed by various Pocket PCs. Peanut Press became Palm Digital Media and rolled my growing e-book library over so I could still access my purchases. Then eReader took it over and my library survived that move, where it still lives today even though eReader is now a subsidiary of Barnes & Noble.

There are almost 500 books in that library, all of them read and enjoyed over the years. I visit them from time to time to reread personal favorites, an ability I hope never disappears but truth is the entire library could disappear at any time should B&N choose to take it away. I shudder to think about that possibility, but it's a fact of digital life.

These days I get my e-books from the Kindle store, as I appreciate how easy it is to shop for them and read them on multiple devices with WhisperSync keeping my place automatically. I read on tablets, PCs and smartphones without missing a single bookmark. My Kindle library is growing steadily, and will rival the size of that original collection before too long.

I imagine there are quite a few e-book readers like me, who have gathered a large collection of books that crosses multiple online retailers. While online collections are easy to maintain when only one retailer is involved, it's not so straightforward when books have been purchased from multiple retailers. That turns a simple collection into multiple libraries that don't talk to one another, and for voracious readers that can lead to the dreaded situation of buying a book that has been already purchased (and read) on another retailer's site.

There must be a convenient digital method to keep track of multiple e-book libraries, but I haven't found it yet. How about you? Do you have a method to track multiple e-book libraries that is easy to implement and maintain? TalkBack to me about how you do it.