A great resource I have found is Aozora Bunka. This website has over 10,000 public domain books, or books that the authors have allowed to be distributed online for free. You can search by author or title, and all of these books can be saved as .xhtml, or as a plain text file. With a single tool that many Kindle owners may already have, you can now have "native" Japanese ebooks on your Kindle! If you are looking specifically for children's books, check out a collection of them at Fanta Jikan and click the ">>青空文庫テキストへ" then follow the steps from step 5.
Here are the steps:
1) Download the ebook manager Calibre
2) Go to Aozora Bunka and find your desired ebook.
3) Scroll down to the bottom of the page until you see a .zip, .html, or maybe .ebk file
4) Click the ".html" link.
5) Right click in the webpage and save as an .html file to your computer
6) Open Calibre and click and drag the downloaded file into your Calibre Library
7) Right click the newly added ebook and add to device (make sure your Kindle is connected) and it will auto convert it into a file usable by your Kindle.
You now have a flawlessly working Japanese ebook!
Things to note:
- Of Amazon's devices, only Kindle Keyboards (aka Kindle 3) and higher are able to display Japanese fonts
- Furigana is displayed in either << >> or ( ) after the kanji in question
- There is no text-to-speech option for Japanese text
- You cannot lookup words in a dictionary
- Text is displayed horizontally
This method is much easier and produces .pdf files optimized for the Kindle's screen. The file produced is made to be read in a traditional vertical manner. It also preserves the furigana and properly displays it next to the kanji in question. If you don't highlight passages and make notes, this option provides a very clean alternative.
1) Go to Aozora Bunka and find your desired ebook. For example, here is Hell Screen by Ryunosuke Akutagawa
2) Scroll down to the bottom of the page and copy the link of the .zip file
3) Go to the Aozora to Kindle website and paste the link into the space provided.
4) Click PDF化 and the file will be saved to your computer.
That should produce the .pdf file, now add to your kindle!