http://www.amazon.com/Rings-That-Bin.../dp/0967789443
this is 'rings that bind'. no curved piecing. the price on amazon is crazy. the book is $24.95.
on the picture of the book, click on the choice for the back cover to see the possibilities. it's done like a flippy thing with the addition of machine applique.
google 'rings that bind' for other info.
edit: i just thought of a good comparison. it's done like a fake 'orange peel'. exactly the same with your choice of back and front. the back has the rings that turn over to the front.