It doesn’t need much. Audiobook Mastering will bring up the volume with little or no sound damage. Again, in my opinion, Jim has a quiet enough background noise that he can back away a little bit with no serious problem. He passes Noise at -76dB. The fuzzy rule is to be able to pass at -65dB and the actual drop-dead limit is -60dB.
https://forum.audacityteam.org/t/audiobook-mastering-version-4/45908/68
What microphone are you using for this work? That high quality is unusual for home readers.
I can listen to a story in either of those voices.
Koz