Google TTS Wavenet voices for Android (Text to speech engine).
I read a lot of ebooks. The problem is that I get tired easily. Listening to ebooks is better for me. I use Google Books Text to speech feature all the time. It works nice, but the voices are terrible.
I even bought some premium TTS engines like from Acapela. It is bearable but lets get stright. These voices still sound like robots. OK for navigation apps but annoying for ebooks.