Book card designs, I can't decide...

Authors use their imaginations to create fantastical worlds and characters that live in these worlds and interact with one another in such a way that the authors' readers experience theses amazingly crafted realities so that they feel they are in the moment of what they are reading. The time comes after an author gets published not once, but twice, and promo items need to be designed. Don't misunderstand my dilemma, it's a great dilemma to have :) I need to figure out while designing book cards for Betrayal Bites, book 2 in the Sydney Sedrick series, would having both book covers on the front be nore eye-catchy than just one? Need input :)