I understand "Dont" to mean the same as "duquel"/"of which", so I was wondering if the "en" is still needed in the subordinate clause, as the relative pronoun "dont" is already referring to the books?
Example:
Je lis beaucoup de livres, dont il y a beaucoup ici.
Example:
Je lis beaucoup de livres, dont il y a beaucoup ici.