If you loved the way Declare meshed Cold War espionage with occult conspiracies—where a spy like Andrew Hale uncovers supernatural threats behind real-world conflicts—you'll be hooked by The Atrocity Archives. Here, you'll follow Bob Howard, an IT specialist recruited into a shadowy government agency, as he faces Lovecraftian horrors and bureaucratic intrigue with equal parts wit and paranoia. The blend of spycraft, cosmic threats, and secret history is pitch-perfect for fans of Powers' supernatural espionage.

If you enjoyed how Declare weaves together real historical events with secret supernatural agendas, you'll be fascinated by Foucault's Pendulum. Eco's novel is a labyrinthine journey through centuries of occult conspiracies, blending fact and fiction as three editors unravel (and invent) hidden connections across history. Like Powers, Eco blurs the line between myth and reality, keeping you questioning what’s truly at stake.

If the mysterious, reality-bending powers behind the scenes in Declare drew you in—where the true nature of the supernatural is both awe-inspiring and terrifying—then you'll be spellbound by Shadow & Claw. Wolfe's world is layered with secret knowledge, ambiguous magic, and forces that shape destinies from the shadows, all revealed through the eyes of the enigmatic Severian.

If you were drawn to the morally ambiguous choices and internal conflicts of Andrew Hale in Declare, you'll be gripped by The Secret History. Tartt’s novel immerses you in a group of intellectually gifted but ethically complicated students whose actions spiral into darkness, mirroring the uncertain morality and psychological complexity that makes Declare so compelling.

If you admired the immersive, richly detailed worldbuilding in Declare—where every historical and supernatural element feels meticulously crafted—you’ll be intrigued by The City & The City. Miéville’s twin cities overlap in the same physical space, each with their own cultures and rules, creating an atmosphere as tangible and mysterious as the secret world of Powers’ occult spies.