Most of the kindle covers offered online and at the store are not cozy or unique so I decided to make my own cover. Hopefully no one takes offense to this, but I used a Nicholas Sparks book for my kindle cover since I just could not get into his stuff.
Destroy your book. In order to make room for your kindle, you'll need to rip out all of the pages inside the hardcover while trying to not damage the spine's structure. I found taking a box cutter to cut the bulk of the pages away from the cover also works well.
Make it cozy. Now that you have a book cover sans pages, it needs a new look and feel. Measure your cover laying completely flat. It should be about 8.5" by 11", so take one piece of felt for the interior of the cover and hot glue it into place. I found that laying a thick line of glue around the edges looked better than trying to cover the entire surface with glue. Press firmly and let dry for a couple minutes.
Close it up. Take the elastic and hot glue the ends together to make a circle. After a few minutes slip the elastic circle over the cover while it is closed so that the elastic can lay flat against the front and back exterior. Use your ruler to position the elastic about a half inch from the edges where the cover opens/closes. Glue generously only where the elastic is touching the back exterior of the cover.
Cover it. Open the cover by moving the elastic over from the front exterior cover. Lay the cover flat and measure another piece of felt for the exterior. Glue into place like the interior piece, but this time you'll need to carefully work where the elastic is secured on the back.
Frame it. Now that you have a basic felt cover, it needs a couple more pieces of felt to secure the kindle so it won't slip out of the side. Take your ruler, cutting board, and rotary cutter to cut out a 3" square, and then cut that in half diagonally. Take the two triangles and position where they will hold your kindle in place inside like the first photo shows. Glue into place, and don't worry about leaving enough slack for the kindle to slide in because this will loosen a little with use.
Use it. This is also a good time to adorn the exterior with embellishments if you would like. I suggest fabric paints, appliques, sequins, studs, etc.