ESSENTIAL for ALL authors: you must have an independent website about you the author and your book(s). Even if you sell through Amazon and Kindle you should promote your books on your own site or page for independence.
For direct selling and earning more than an Amazon sale
For publicity, news, promotions, contacts etc
These days with WordPress it’s easy; if you’re a writer.
A book that tells you how and tells of the wows of Amazon only reliance and with lots of hints and tips for promoting you and your book(s) – see The Book-kit.