I used 4 colors of yarn, and made the pouch large enough to hold a small paperback book. The pouch could be easily enlarged to hold bigger books, or line it and use it has a purse.

You will need a button similar to the one I used, or some other way to fasten the flap closed, either buttons, or magnets, or other sort of clasp.

You can experiment making this with either 2 or 3 colors instead of 4.