I think the Ops Teams is a bit funny here. Because you can already always download the whole planet file incl. history since ever. AI should use this instead of DDOSing the OSM main website.

The easiest way for me is the Mapcomplete theme for bookcases: https://mapcomplete.org/bookcases.html With this, besides finding, you can also maintain existing ones.

(and i do not know a good way to find bookcases directly on osm.org without the help of e.g. overpass)