Whenever I come back to Japan i buy lots of books. Literally lots of them.
It'd be really nice if Japanese books are available for Kindle, or Sony Reader or whatever eBook device. The Japanese book industry is crap (like their movie/music industries are) and it probably needs another 5 years or so for them to finally adapt to the technology.
They also have their ridiculous no-repricing regulation that doesn't allow selling books in lower price, which I suspect breaks the antitrust law.