When recording an audiobook, should I be recording the entire thing as one track, or should I have multiple files for every single chapter?
One of the things I’ve seen that ACX QA people like is when all the audio is put together well. One track sounding the same as another track. Does that mean I should master everything altogether at the same time and then split the file up into chapters? Or do I just make sure everything has the same settings?
Well, I don’t know if it’s proper, but this is what I’ve found works for me so far with ACX’s requirements.
ACX requires a separate file for every thing, and a fifteen minute audio sample for the author (doesn’t have to be exactly fifteen minutes, just a good idea of the work), and also a 5 minute sample for potential buyers to listen to.
This means separate files can be good. I’ve been doing them that way and so far, so good.
To make the 15 minute sample, I just imported tracks in audacity to fill up the 15 minute mark, then removed the clip boundaries, and mastered everything together.
I think the separate files makes a lot of sense too, even if you want to master every file at the same time, together, to give it a more consistent tone since you can mix the files together in the end if you really need to, then piece them back out. Although, with proper technique, you will probably keep a consistent tone naturally as things go along.
ACX posts clear submission requirements.

https://www.acx.com/help/acx-audio-submission-requirements/201456300
They want all the chapters or sections to match. They hate distractions such as changing voice or rooms in the middle of a book. Making a “Studio” or a place you always record is important. That’s also why you need to settle on a reading style, quality and acceptance before you start a book.
It’s a new user mistake to read a whole book and only then submit a test to make sure everything is OK.
There was a poster who moved houses in the middle of a book and wanted us to make the two readings match. I don’t think we got it to work. The readings were too different.
Koz
There is very little in our posted Audiobook Mastering process that can change the quality of your voice.
https://wiki.audacityteam.org/wiki/Audiobook_Mastering
You are much more likely to have trouble by reading some healthy and some with a head cold or changing rooms or microphones in the middle of a show or book. We can’t fix those later.
If you set up a Kitchen Table Studio…
https://forum.audacityteam.org/t/too-compressed-rejection/52825/22
Use the same kitchen table every time.
Koz