Select your work. Analyze > ACX Check.
DB values work like this.
https://forum.audacityteam.org/t/audiobook-mastering-version-4/45908/68
Noise is the one that drives home audiobook readers nuts. Good luck.
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Do Not read the whole book and only then try to “fix it” to pass standards. Read a short segment and see if you can make that work. If you can’t, post back.
Koz