I downloaded a podiobook at the hospital yesterday onto my Kindle. It downloaded, but it took me a while to find it once it disappeared from the downloads place. Finally I found it under music but it said it only had two of the "songs." This afternoon the rest of the episodes appeared in the music section.
This doesn't sound efficient, but last time I tried this I totally filled my Kindle storage because I couldn't figure out where the Kindle had put it so downloaded it over and over. And over. So I did better this time and maybe it will be quicker next time.