All Star Superman #2

Frank Quitely's cover for this 2006 DC gem draws you in with a quietly tense composition: a wide-eyed young woman clutching a small device with a glowing green light stands at the threshold of a doorway, her expression caught somewhere between wonder and alarm, while Superman himself — seen only from behind in his red-and-blue suit — faces a sprawling, shadowy room packed with mysterious machinery and hanging chains. The cover's tagline, "Can YOU guess the secret of Superman's Forbidden Room?", makes the whole thing feel like an irresistible puzzle. Grant Morrison and Quitely were clearly having a lot of fun playing with the idea of Superman as a figure of genuine mystery, and this issue wears that intrigue beautifully.