i looked it up and they seem to be supported but its a matter if apple will let you use outside sources for your books so idk heres the link tho hope it helps http://support.apple.com/kb/ht4059
I dont use them on a kindle but they will work heres a link so you can see for yourself! happy new years eve! https://kdp.amazon.com/help?topicId=A2GF0UFHIYG9VQ