The answers provided here are quite helpful, but they don't address a particular concern that I have. What if I'm not in the US? Where do I pay tax? Do I have to pay tax in the US and in my home country if I use kindle to self-publish a book?
You pay 30% US taxes by default but may get a reduction if your country has an income tax treaty with the US. Most Western countries do. I am in the UK and get a 100% discount because of the treaty between the UK and USA. Here's the list of countries:
As for your NET (after any US tax) royalty earnings, you'll need to declare them on your own country's annual return as income (either individual or company) and get taxed on them in the same way as any other earnings.