Here's an easy, durable book cover you can make that requires nothing but a paper bag and scissors.
Step 1: Materials
This is easy, you only need a couple things:
1) Paper bag
3) A book
Step 2: Cut apart the bag
To start out, cut out the bottom of the bag and make a cut down the length so you have one big rectangle.
I prefer to cut down the seam in the middle of one side (see other pic) so that it won't be visible when you're done.
Step 3: Cover length
To get the proper length of the cover, lay the book on the paper and fold over the first edge around the inside of the front cover so that it's an inch or 2 away from the binding. Then fold it around the back of the cover in the same way. You're gonna have some extra, so mark where it's a inch or so from the binding when the book is closed and cut off the excess.
Step 4: Cover height
Now you need to fold the top and bottom to the size of the book. I used an existing fold along the bottom to start out. Then I use the book as a guide to mark the height. Line up the book with the bottom of the cover. Then fold up the top overlap. Do that the whole length of the cover and then fold it down.
Tip: if the bag has a label on it, make sure it's on the inside.
Step 5: Put it on
Slide the paper cover on so that book cover is inside the folds. It'll be a tight fit so wiggle it on if you need to.
Step 6: You're done!
That's it! Now you have a blank canvas to decorate your books. You also get a handy pocket in the front & back where I tended to stuff my syllabus & notes. I found markers & pen work best. But feel free to use stickers, paint or whatever you want to make it your own. Enjoy!