Let's be clear, a so-called perfect mystery for suspense junkies almost always starts with a clock ticking. That's the baseline. A puzzle alone? Sure, that's nice for a cozy afternoon, but suspense needs stakes that strangle you. It's that trapped feeling in 'Gone Girl' where you're not just figuring out what happened, you're terrified of what's happening right now to the characters you're stuck with. The narrative has to feel unstable, like the floorboard giving way a little more each chapter.
What absolutely ruins it is when the author plays totally fair. I know, blasphemy. But an airtight, solvable-by-clues puzzle often deflates the tension halfway through. The perfect suspense mystery lets you think you've solved it, then makes you doubt your own reasoning because a character you trusted just did something inexplicable. It's less about the 'who' and more about the creeping dread that the 'who' might be the person narrating the story.
A lot of newer genre-blends get this right. Mix in some domestic dread or a dash of corporate horror, and the mystery becomes about surviving the revelation, not just announcing it.