One thing that has really bugged me about the Kindle vs real books is not having the back cover to reference. When I'm faced with a shelf full of books it's hard to make a choice just based on a cover (which is all you have with the Kindle). I miss the back of the book! I finally came up with a trick to help me both sort my books a little (since the Fire doesn't have any real way to organize your books beyond alphabetical or author) and I thought I'd share it.
The Back of the Book
When I download a book it's because the description was good enough to make me want to read it. So now, after I purchase the book, I open it in the "Cloud Reader" (which opens the book in your browser. I click on the first word on the page and then add a note (the highlight/note option will pop up when you click on a word). In the note I put the category of the book followed by a copy/paste of the description provided on Amazon.
Now, when I'm looking for something to read I can either do a search for a particular category I might be interested in. Or I can just scan the covers then open the book and read my note to "view the back cover" and see if it's something I'm in the mood for at that moment.
If you already have a huge collection of books you can easily update your books via "Manage My Kindle" on the Amazon website. Just load up the list of books. Click the plus sign next to the book and open the "book details" in a new tab, to get the book description. Then on the right hand side of the screen you'll see an "actions" dropdown. Select "read now" to open it in the "Cloud Reader".
While you are at it, leave yourself a comment in your note about those books you've read and what you thought of them to help you remember later.