Do not let your books lean at an angle. This causes "shelf sag" (damage to the binding joints). Use bookends or pack the books snugly—but not too tight. You should be able to remove a volume with one finger without prying.
I’m missing details to proceed. Do you mean: boek collections
Pick one of the numbered options or give brief specifics and I’ll produce the full deliverable. Do not let your books lean at an angle
Focusing on specific eras, such as Enlightenment philosophy or Post-modern literature. boek collections
Drawing from Nassim Nicholas Taleb’s concept of the Antilibrary, a deep feature of a profound collection is the ratio of read to unread books.
If you are looking for articles about collecting books, several professional resources offer guides on curation and maintenance: