The place where the Thieves' Guild was located had no magic to repel dust, let alone inside that bookstore.
Hill merely glanced at them to tell the thieves inside that he knew they were there and was not pleased, so they better understand what was happening before getting retaliated against.
"Respected Archmage sir," Somer cleverly changed the subject, "there are quite a few books today. Many people have only come back as the deadline approaches.
Moreover, there are more duplicates this time than in the past few days."
Hill nodded, "No matter." He of course knew that many duplicates would appear, but without doing so, most ordinary adventurers who were illiterate wouldn't be so eager to procure books.
And their peculiar behavior, of course, would attract a lot of attention; there would always be some scions of wealthy families with abundant collections willing to sell their books.
The prices Hill offered were unprecedentedly high within the Ten Towns of Icewind Valley.