Booklive.jp is a website which sells Japanese E-books (電子書籍, “denshi shoseki”) from a wide variety of genres, including magazines, manga, business books, and adult material. While the layout of the site is a bit cluttered, its pretty easy to get used to if you know Japanese (I don’t think they have an English version of their site). Even if you are just learning the language, I think finding your way through the site to find a book you like is a good way to learn some new words in context.
Besides the pretty large selection (they boast almost a quarter million titles, exactly 231555 as of the time of this article’s writing), whats great about this site is that many (all?) of the works allow you to browse part of the book. In Japanese this is called “tachiyomi”, and you can do this from the site via the buttons ブラウザ立ち読み (browse from web browser) or アプリ立ち読み (browse from mobile app). If you want to browse a book from a mobile device, you need to install their mobile app. Doing this on iOS (iPhone/iPad) required me to change my store settings to the Japanese store. There are various sites online which give details on this but you can start here.
Besides iPhone/iPad, Boolive also supports Android devices as well as windows desktop. There doesn’t seem to be a Mac OS X client, but you can read via the web on Safari or some other browser. They also support an E-book reader called Lideo, but I think it is only available in Japan. Unfortunately there is no direct support for Kindle, though I think this is more due to restrictions created by Amazon than anything else. There may be a way to convert files for use on a Kindle but I haven’t figured out how.
Booklive also has short term sales where certain books will have their price reduced for 2 days. These are accessible via the “2-day” tab on the site. I’ve seen manga which are normally go for around 800 Yen drop to around 100 Yen.
For the few books whose prices I compared against Amazon Japan, they were about the same, although these were all non-sale items.
An avid reader since I was a boy, I still love the feel of physical, paper books, but with the many advantages of E-books it’s tempting to never buy a real book again.