Okay, I've searched through the boards and online at DTP and even bought two Kindle books to inform me but I still can't find a definitive answer to my question (I do find lots of differing opinions), so here goes:
What are the preferred dimensions for Kindle cover art that is uploaded to the website, in the first step of the process? (the cover art that is shown on the amazon web page)
And, what are the preferred dimensions for cover art inside the book (to be displayed on the Kindle screen) and should it be grayscale?
I just scan a book cover and upload the thing. Somewhere in this mess I have a printout of Amazon's requirements, but I haven't looked at it lately.
Aha! Here it is:
1. Tiff or jpeg
2. 24 bit RGB
3. 648 pixels tall (9 inches tall at 72 dots per inch)
I don't include cover images in my e-books, so you are on your own there. Yes, they're grayscale as seen in the Kindle. I think however that they show in color in Kindle for PC or on the Apple Toys, but I'm not sure of that; none of the books I have read on my iPhone have any images whatever, including the cover. (I see a cover thumbnail on my Kindle for iPhone page, but none in the book itself. These are all free downloads. I'm not a big one for actually paying for things.)
I read many comments here that color covers look terrible as seen on the Kindle. You might have to experiment to discover whether grayscale produces better results than uploading the color version and letting Kindle mangle it.