You can format your book so that it appears one way in the e-ink KIndles and another way in the Fire (and increasingly in other devices and apps). However, it takes a lot of knowledge of html and style sheets (CSS). Do a search here for CSS, and especially pay attention to posts by MrsLasers.
As Kindle books are formatted now, they contain two files, one for the standard-issue Kindles (Kindle Format 7) and another for the new ones (KF8).
Well actually, it is necessary in my situation. I don't exactly make books. I work for a company called Barcharts (feel free to look them up) and their product isn't exactly linear text. There is a great deal of formatting and graphic content. I know that you can separate the stylesheet so that depending on what reader the user is using it will display the correct styles. I have tried making a single ebook with the stylesheet being parsed for different readers, but when it comes down to it the ebook coded for KF8 has too much "flexibility" for me to code for both.
Despite the fact that it would be better to just make ONE format that is compatible for all devices, do you know of a way to upload 2 formats?
Alas, no. I suspect it can be done, because I've heard of books that are specific to one format or the other. Perhaps it's something available to mainstream publishers but not to us.
I realize I was wrong about there being two versions of each Kindle book in a download. The clever rascals at Amazon know which Kindle you're downloading to--KF7 or KF8--and they supply that version only. It also follows that those who complain that their file size has been doubled are wrong about that: there should be no difference in delivery cost between the new KF7/KF8 duality and the old KF7 download.
(It's possible, I suppose, that one could trick out the KF8 version to such an extent that it might cost 15 cents more to download. Hard to believe it could be much more than that.)