I'm not sure how books work, but in the world of piano sheet music, there is a copyright for the music, and one for the editing/publishing of it. Or at least that's the way I understand it.
e.g., All music written by Frédéric Chopin is public domain. He is long dead. His compositions are public domain. However, a copy of it that was edited and printed within the most recent decades is not public domain (unless the editor/publisher releases it that way). You are free to look at Chopin's compositions and edit/print your own. Which is what sites like "The Mutopia Project" have done. Individuals on that site take public domain music, edit it and create printable versions, and release those free for everyone to use.
https://www.mutopiaproject.org/
Compositions are VERY professionally laid out on Mutopia:
Example (one of my favorites to play):
https://www.mutopiaproject.org/ftp/C...t_minor-a4.pdf
I would assume books are similar to music. You have a copyright for the original manuscript, and then a separate copyright for the editing/publishing step.