So here’s something I whipped up recently:
Until this week I’d been using a legwarmer and twisties to keep my Kindle safe, and now it finally has a real case. I think there are more interesting designs out there, but I wanted my case to be thin and easy to get in and out of a backpack or messenger (i.e. no buttons or other snag-able bits).
The whole thing is basically one long rectangle that’s been folded over itself, and the sides are stitched shut. You pull the top back, fit your Kindle in, and pull the “cap” back over. It stays shut with no buttons or clasps or anything since the swatch overlaps in the front.
Pattern: For a 4th generation Kindle
Materials: 5mm hook (US: H), worsted yarn, yarn needle
Begin with a slip knot and chain (ch) 17.
Row 1: ch 2, single crochet (sc) 17 
Row 2-66: ch 1, sc 17 
Fasten off and weave in ends.
Decide how where you want the opening in the case to be. Top flap: ~10 rows. Have the top flap overlap with front part beneath it by 4 rows. Pin in place with a hook or yarn needle. Before sewing the side seams, wrap the project around your Kindle to check size.
Using yarn needle, double yarn for extra thickness. Start at top and stitch down one side. I used a whip stitch. Where there are three layers of swatch, be sure to stitch through all three layers. Tie off at bottom. Repeat for other side.
Now you have a snug new Kindle case.