Mostly what VyderScope said, but also: I wouldn't panic too much about keywords inside the ebook metadata. Despite all the blog articles saying how important the ebook metadata is, as far as I can tell very few places use the ebook metadata in any consistent manner*. The keywords you need to worry about are those on your website/blog and any keyword fields offered by your distributors.
* Probably because the "standard" is only standard about the highly technical bits, and ignore all the truly useful and practical aspects - like how to implement formatting for descriptions etc.
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