Like @mr_monkey explained here: https://community.metabrainz.org/t/import-data-from-bookogs-and-comicogs/487094/16 the database has a separate section for imported data, so each entry will be marked as imported and then needs to be validated or can be discarded.
Once bookogs is finished, I think comicogs will be easier. But as for bookogs, a good way to import series is missing.