Wow, that is absolutely phenomenal! This alone makes me want to listen to the audio book, which would be my first. Perhaps a dumb question, but are ambient tracks and/or similar fx stuff common in audio books? I'd always assumed it was simply a reading.

Many audiobooks have brief music interludes between major sections, but generally that's it, just narration.

Soundbooth Theater does exactly that with music and sound effects

https://soundbooththeater.com/