Some of his books are still in print and available new. Many are available used for prices varying from not-so-bad to forget-about-it. Warning, some are Japanese language only. Once you understand the basic concept, you won't need written instructions for the patterns, but don't buy a Japanese one for starters!
My personal favorites are these two. I lovelovelove the first one. Page after page of wonderful, amazing, unusual Christmas designs. The second one is my go-to reference for sliceform design. It's all about making the shapes, not completed projects.
This one looks intruiging. I can't vouch for it personally as I haven't gotten my hands on it, yet . Note it is in Japanese. If anyone has it, or buys it, give me a review, okay?
Here is a selection of his available titles, and a couple by Keiko Nakazawa, his collaborator.