As the title says, after seeing his Book again it's oddly reminiscent of the book skill on Greed Island. We know Ging used criminals so it's not unrealistic to assume someone like Chrollo could be involved. We also know how strong Chrollo is Ging may have approached him for his strength and skills. Idk but Hisoka's reaction to Chrollo bringing out his Book reminded me of how they'd react when an opponent summoned his book on GI.