Paperback book cover

With the weather cooling down I'm doing less bike commuting and more bus commuting. Bus commuting = reading time. I wanted to take better care of the paperback books I read on the bus, especially the ones I am borrowing, so I devised a book cover:





I love it. It's thick enough that it protects the book from getting bent up and bruised in my purse, but it only adds a few millimeters to the bulk of the book. And the inter-office mailing envelope type closure means it will fit books of almost any thickness.  As long as the books are of the same format. I learned there are, unfortunately, three different formats for paperback  books:

A Format paperbacks are 110 mm x 178mm (4.33" x 7.01")in size,
B Format paperbacks are 130 mm x 198mm (5.12" x 7.8"),
C Format (trade paperbacks) are 135 mm x 216mm (5.32" x 8.51")

Doh! Guess I'll be making 3 different sized paperback book covers.