I've been using Tortoise TTS[1] to narrate the sci-fi novel I'm writing (alpha readers wanted, see profile for contact):

    $ find audio/ -type f -name "*combined*wav" | sort -n
    audio/01-xander/xander_combined.wav
    audio/01-yuna/yuna_combined.wav
    audio/02-xander/xander_combined.wav
    audio/02-yuna/yuna_combined.wav
    audio/03-cassandra/cassandra_combined.wav
    audio/03-yuna/yuna_combined.wav
    audio/04-xander/xander_combined.wav
    audio/04-yuna/yuna_combined.wav
    audio/05-cassandra/cassandra_combined.wav
    audio/05-yuna/yuna_combined.wav
    audio/06-cassandra/cassandra_combined.wav
    audio/06-yuna/yuna_combined.wav
    audio/07-xander/xander_combined.wav
    audio/07-yuna/yuna_combined.wav
    audio/08-cassandra/cassandra_combined.wav

I started the task on March 10. My NVIDIA T1000 GPU (no joke) has been chewing through the prose non-stop. There are 12 chapters written so far, with the computer narrating about a chapter a day. I can't share the audio for legal reasons (celebrity voice snippets plucked from YouTube interviews), but the output is nearly human in quality, though there are numerous glitches in the o̶u̶t̶p̶u̶t̶ matrix.

Here's the script that launches Tortoise TTS:

    for i in $HOME/.../chapter/??-*.txt; do
      F=$(basename $i);
      VOICE=$(echo ${F%.*} | cut -c 4-);
      CHAPTER=$(echo ${F%.*} | cut -c -2);
      D=$(dirname $i);
      CLIPS="$D/../audio/$CHAPTER-$VOICE";
      mkdir -p $CLIPS;
      ./scripts/tortoise_tts.py -O $CLIPS -v $VOICE < $i;
    done

[1]: https://git.ecker.tech/mrq/tortoise-tts