Yay, I'll have to try this on my Echo. I for one am not a fan of audiobooks overall. I just can't get into the story like that, I tried again and again. I have a handful of them to listen to from time to time. Done that with Echo too.
But occationally I need to do something around the house and I'd still like to hear the story at the same time. Its not worth it to get expensive audio books just for that case and many of my books don't have audio books anyway. It fills a gap for me. TTS that is. The voice has gotten much better than early kindles for sure. I also prefer to listen to stories with the least amount of "drama". I think its partly the acting of the stories with audio books that keeps me from getting into them.
I also don't have any issue with my Echo not understanding me or the other member of the house. We did voice train it as its suggested at the start. Only time it has issues hearing is when we listen to surround sound stuff. Not Echo fault as one of the side speakers is 1 foot away from the Echo where it sits on a side table right now. It can't pick up my voice if a loud music sound is screaming in its ears after all.
Off to figure out how to do TTS..