[CRussel]

I also use Voice -- it works well, but does require you to load the book onto the device first. I'd prefer something that could do its own load from a Cloud provider -- on my iPhone I use Bound, which allows me to load directly from my OneDrive. Of course, my first and primary audiobook reader on both Android and iPhone is Audible.

ETA: Another one I've used is Smart Audiobook Player. Works well, with a full-featured trial, and then $1.99 or revert to a somewhat stupider version. Even the stupid version works well, but if you're on a device that doesn't have the Google App Store, it's your only choice -- the $1.99 can only be done through the App Store.