Coloring books are great. They provide a fun opportunity to not only color, but trace and draw as well. A Sonic X coloring book would be a great thing to learn with!
The inside is loaded with lots of line art from the show that you can color in or trace onto other paper. It likely has single character shots, scenes and various lesser-seen characters. In 2009, you can sometimes buy this from www.atamii.com --however, it does go in and out of stock because people like the item so well and it IS an import. Where could it be found naturally in Japan?