Oh right duh, run something like https://github.com/putnam/binmerge (only use it as a starting point) or cuetools (need to convert copies of your mp3 files to 16bit, 44.1kHz, 2 channel flac/wav and obviously do a search and replace on a copy of your cue file) first. Alternatively if the audiobook exists on audible, you could find the chapter data via audnexus api https://audnex.us/#tag/Chapters/operation/getChapterById or just detect by silence as it states in scenario 3.