Amazon Japan will ship books to the United States. They come fairly quickly. I have used it in the past when I needed a book and wasn’t making a trip to Japan in the near future. We do use it at work when we have rush requests.
Amazon Japan’s Kindle Store is not available to people who do not have a Japanese address. This is unfortunate, but it is life. There are a small number of Japanese books in the US Kindle, but very few.
I really love this online bookstore for locating books. I used to be a big fan of Junkudo and used its online bookstore to order books and have them held for me at a store closest to where I would be staying during my Japan visit. Junkudo has stopped its online service, Honto.jp is the online shopping presence for Junkudo, Maruzen, and Bunkyodo. I really do find it easier to use and gravitate to honto.jp for book searching over Amazon.jp. There is an ebook component and a print book component to the website. It is possible to register without giving any credit card information or personal details, and download the free books. I see from the website that it advertises a service called Buyee – an online proxy shop for people wanting to buy Japanese things (like from Yahoo Auctions) from overseas.
I just revisited Honto.jp to figure out why I haven’t been using this for Japanese ebooks and found that it is not a good store for me as a resident of the United States to use for a couple of reasons. For the print part, I would have to use a proxy service to buy and deliver the books for me. For ebooks, I can use the honto app on my Mac, but there is not one for my iPad/iPhone and that is a serious drawback because I really enjoy using the dictionary feature on the iPad/iPhone and now that I have started using the dictionary lookup on my iPad I am not giving it up.
Kinokuniya has both a physical and online presence. It also has its own proprietary browser called Kinoppy. In theory Kinoppy books are available to users outside of Japan – one of my students used it – but I have also read that the number of titles is very limited. There is a separate search engine for overseas users. So I am on the fence about this one and would appreciate feedback.
eBookJapan is the service that I used the most until recently because it let me use a US credit card and had lots of books and manga that were free or had good previews, But when it was bought out by Yahoo! Japan and newly purchased books no longer download into the app. I much prefer reading on my iPad than the monitor or my laptop, so this makes eBookJapan less appealing to me.
The BookLive reader says that it is available either through the Apple App store or Google Play. I am not seeing it in my App Store though. It is possible that it is only available through a Japanese login. I tried using the preview feature on my iPad, and am unable to get the dictionary feature (press your finger on the word you want to look up to invoke the dictionaries) to work. So this makes it less useful to me.
BookWalker 日本ストア is my current go-to site for Japanese ebooks. It is very clearly aiming at a light novel and manga crowd, but it contains much more than that. For the zine folks, you will find 同人誌 available there. I have found most of the books that I would have bought in print here, and now that I am not making frequent enough trips to Japan to be able to stock my shelves with Book-Off priced books, I can still satisfy my reading urges here. And, more importantly, the viewers works like a charm.
The BookWalker Global Store is for English language books and manga. It really looks like it is for light novels and manga. One of the things I really appreciate about BookWalker Global Store is that it provides the Japanese title for translated works so that I can go back and easily locate the original. Also your login and bookshelf are the same for the Japan and the Global Store, so it is all neat and tidy.