What country are you in? Some countries can't use the link I provided you have to use your country's Amazon site. But if you are in the US use this link: https://www.amazon.com/Speak-Japanese-90-Days-Becoming-ebook/dp/B014RTDPBA?ie=UTF8

There should be the option to get the Kindle (free) or paperback (not free). Click the Kindle link and check out on the right (this is how it appears on desktop it may be different for mobile)

If that doesn't help let me know.

Edit: a word