Movies like Sinister

If you want that specific blend of obsessive investigation into documented supernatural evil where the protagonist's need for answers becomes their undoing, Stir of Echoes and Fallen probably track closest—both feature skeptical men compulsively unraveling mysteries that exact a price steeper than knowledge, with the same sense that some doors shouldn't be opened. The Conjuring and Dark Awakening may scratch the itch for dread that accumulates through meticulous discovery within a cursed space, though they're less focused on the investigator's psychological descent. The found-footage options (616 Wilford Lane, The Poltergeist Diaries, The Black Gate) approximate Sinister's suffocating atmosphere of evidence that implicates rather than explains, but they tend to distribute dread across a family rather than concentrate it through one man's obsession.