I had the same challenge recently. See the attached. The individual parts are in a "/parts" directory. The "book.ly" file assembles the parts into a book with TOC.
I've also attached a simple script (assemble_book) to generate the book.ly file (unix bash). I am a newb with lilypond, so I'm sure there's a better and more natively lilypond-ish way to accomplish this. I hope someone else will chime in. -charlie
01. part1.ly
Description: Binary data
02. part2.ly
Description: Binary data
book.ly
Description: Binary data
#!/bin/bash
echo '\version "2.24.3"'
echo 'bookTitle = "book of parts"'
echo '\markuplist \table-of-contents'
ls ./parts/*.ly | while read partFile; do
echo
echo '\include "'${partFile}'"'
echo '\bookpart {'
echo ' \header { title = \pieceTitle}'
echo ' \tocItem \markup \pieceTitle'
echo ' \score { \scorePart }'
echo '}'
done
