I love mystery games, so--

Love: When mystery games actively draw attention to the idea that you need to draw your own conclusions about what you find in the game, and make your own truth, instead of just following a track

Hate: when the above is expressed as a formalized "Mind Palace" mechanic à la the more recent Sherlock Holmes games. That's just covering the track with a tarp instead of letting you build your own theories. Either let people accuse who they want with the evidence they have (once again I plug Paradise Killer) or acknowledge that there's only one acceptable answer