https://itunes.apple.com/us/app/kybook/id673027171?mt=8
https://itunes.apple.com/us/app/audi...320694795?mt=8
I use downloads-free app to open zipped mp3 folders from dropbox, so you can use it for mp3 audiobooks too or probably any other mp3 player.
https://itunes.apple.com/us/app/down...ee/id475190096
Just checked and saw that on my iPad m4b audiobooks (in dropbox) can be opened with OPlayerHD Lite and Documents by Readdle.
https://itunes.apple.com/us/app/opla...eo/id385896088
https://itunes.apple.com/us/app/docu...ee/id364901807
I can also use oplayerhd-lite to read ogg audiobooks and to transfer them directly from my PC/notebook over my WiFi router using browser or ftp, because for some reason dropbox didn't offer oplayerhd-lite as player to open ogg files in, as with m4b audiobooks.