I can't believe this book has been out for several months and no one did a review yet! I LOVED "Patchwork Puzzle Balls", bought a book on Temari (the threaded balls) and didn't like that one bit. Kimekomi - Japanese for "tuck in" - is very cool and fast fun if you're into instant gratification! :) Also called quilt balls, these make fun tree ornaments or bowl/table accents.
The short version? Take a smooth foam ball, use a hot knife to cut your crevices/tuck lines, cut little fabric shapes slightly larger than the lined areas, and you guessed it, tuck it in the slit! My first attempts using an exacto knife and a butter knife for tucking came out OK but had the down comforter puffy look. Do it the "right" way with a hot knife and tucking tool and it comes out a thousand times better, neater, and smooth like the photos.
Tool & Supply tips:
A "hot knife" is basically a not-so-sharp exacto knife tip on either a woodburning tool or the mini craft iron II, you might even have it already if you own either of those tools. Makes a nice, straight and smooth cut in the styrofoam ball. That was a new tool term for me so I went running around looking for something by that name before having a Duh! moment.
plasteelcorp sells smooth foam balls, any size will do, just remember bigger=heavier if you're doing Christmas ornaments! Up to 6" should be fine unless your tree is really wimpy or you go nuts with the glue and ribbons on top! Majority of book patterns call for 3" balls if you want to be ready when your book arrives.
Web search for Kimekomi "tucking tool", or "tucking spatula" and they are common enough. I got one for $5.50 + S&H
I hope you give the book a try, have fun!