Do you have the “low cut filter for voice” that is mentioned on this forum in several places?
I’d leave that out. Unless there is a significant problem with your recording environment or recording equipment there should be no need for a high cut filter. If there is a problem, it’s much better to fix the actual problem than to try and repair the damage.
Compression may not be required - it mostly depends on your voice and your delivery style. If you do need compression, you should use gentle settings so that the effect is not audibly noticeable. Similarly a little noise reduction can help to lower the noise floor, but again, gentle settings should be used so that the effect is not audibly noticeable.
Assuming that you have a nice clean, well delivered recording to start with, I’d suggest that you try normalizing the RMS level to about -20 dB first, then see where your peaks come. You will probably find that the peak level is a little over -3 dB. If the peak level is just a couple of dB over, then you can use a soft limiter (avoid “clipping” or “waveshaping” type limiters) to reduce the highest peaks to within range.
Settings for all of these effects depend on your recording.
Generally I would not use a Chain for anything as critical as “mastering” and audiobook, but if you have a lot of high quality unprocessed voice recordings, then it ‘may’ be possible to use Chains. Perhaps you could post some raw (unprocessed) sample recordings so that we can see / hear what they need - 10 seconds mono WAV recordings will be sufficient provided that it is representative and contains both voice and “room tone”. See here for how to post an audio sample: https://forum.audacityteam.org/t/how-to-post-an-audio-sample/29851/1