code/game/objects/items/weapons/manuals.dm

/obj/item/book/manual	These are "programmatic books," that is books that are hard-coded into the game. Just for the sake of maintainability, keep information subject to change (as in likely to change SOON) out of the non-wiki manuals as they require PRs to change and it is not an author's responsbility to update manuals if they change a mechanic/recipe/feature referenced in one of them Don't worry about adding them to the library, as long as they're one of these types it is automatically added.
/obj/item/book/manual/wiki	These are programmatic books that source its pages / "content" straight from the wiki That means that this content can ONLY be changed by editing the wiki Space Law and SOP Manuals can only be edited by Wiki Admins

/obj/item/book/manual

These are "programmatic books," that is books that are hard-coded into the game. Just for the sake of maintainability, keep information subject to change (as in likely to change SOON) out of the non-wiki manuals as they require PRs to change and it is not an author's responsbility to update manuals if they change a mechanic/recipe/feature referenced in one of them Don't worry about adding them to the library, as long as they're one of these types it is automatically added.

/obj/item/book/manual/wiki

These are programmatic books that source its pages / "content" straight from the wiki That means that this content can ONLY be changed by editing the wiki Space Law and SOP Manuals can only be edited by Wiki Admins