Use QooApp to download and update on Android. It's a third party store front that gives you access to all region locked Asian Games. I've never had any issues with region while using it.
You can't actually download QooApp from the playstore, so go here and download the apk to your phone. If you've never installed from an apk, it's the same as running an .exe on the computer. As long as you get it from a safe place, you're fine.
Anyway, you have to manually install it by going to your phone storage and just clicking it. It's usually something like "my files" -> "downloads" or whatnot. Just open it like you would a picture or a music file and it'll ask you if you wanna install.
Book is 4000yen, or like 3997yen to be specific. Same price as Amazon.
There's processing fees if you use Paypal so it ups price a little bit.
To view the product to buy I'd suggest installing a proxy like Hola VPN which will let you buy the book. Set to Japan. I'd recommend you make an account and log in before playing with the proxy a bit because it just wouldn't let me log in when I was using the proxy lol.
Everything else is pretty self explanatory I think.
I think you can use proxy and do the same on Amazon but I like using Paypal more so using Bookwalker was more convenient for me, but there's a guide on using Amazon as well. However, the time I bought a book from that it didn't process the order correctly so while I got my book they didn't take my money, so that scared me a bit.
Are they... sold out? They look like they might be sold out... http://www.amazon.co.jp/gp/product/4047307548/ref=oh_aui_detailpage_o00_s00?ie=UTF8&psc=1 http://www.amazon.co.jp/gp/product/404730753X/ref=oh_aui_detailpage_o00_s00?ie=UTF8&psc=1