I use Firefox and sometimes Chrome, on Windows 7.

Amazon's in-browser Kindle Cloud Reader lets you "download" books for local/offline viewing. Where are these stored, given my OS+browser combination?

I've searched the Users subdirectory for my user, and could not find a relevant (separate) file in there, specifically not in the Firefox and Chrome profile directories.

To clarify, the files are obviously not downloaded as-is and are stored in some potentially-obfuscated format, possibly in the browser's local store and possibly elsewhere. The question is, where and how exactly?

(This was the first of this question, but wasn't answered there since it was not the main focus of the question.)