It's a cool idea with a narrating voice but also a very risky move and way more time consuming in development.
You have to consider the people that dislike voiced narration.
So you should answer yourself the following questions first:
Does it actually fit the whole theme?
Do people even enjoy if someone reads the novel for them instead of themselves?
Do I force the voiced narration to be always on or do I give an option to turn it off?
If so, how many of my players will actually use it?
Is it actually worth to make all the extra work just to find out some players or even the majority will turn it off?
How much will my game increase in size ontop of all the renders?
As I said it's a bit risky because people usually click in order to progress.
Yes they can put it on auto, but from my experience most people will want to read at their own pace and not have someone force them to move on. This counts for the auto feature and for when the narrator reads faster or slower as the player.
(Also I think most people have at least heard or played The Witcher and they might have a hard time immersing themselves if Geralts raspy voice moans into their ears

.)
In the end it's your game and you should feel free to put in whatever you want.
But being too ambitious can slow you down or make you feel overwhelmed pretty quickly.
I could also be completely wrong with what I said, but this is my opinion.