This is a feature request:

Can the libraries generated in the Terralith libraries added to the list of structures in which the arcanus books can be found?

I think that adding
"terralith:village/desert/houses/library1",
"terralith:village/fortified/houses/library",
"terralith:village/fortified/houses/library"
to
public List<String> structuresWithBookshelves = Arrays.asList( in src/main/java/dev/cammiescorner/arcanus/core/integration/ArcanusConfig.java should be the trick, but I'm not really 100% certain.

I tried adding those to the config/arcanus.json5 file, but it appears that this file is written by the mod but not read as my changes were over-written when I started the minecraft instance.

Perhaps this is merely an issue that the config file isn't being read? (but rather written/re-written). I tried changing the strings in the mod menu, but they also didn't stick. There are lots of generation mods that add bookcases/lecterns, but perhaps it's isn't just so simple as to be able to add the namespace:structure for each mod as a user might use?

I created a pull request which adds the Terralith, Biome-Makeover, and Structory structures to the list of structures which are handled by this mod.