I’ve run a lot of mystery adventures, and I have three pearls of hard-won wisdom to bestow.
@RogerBW is right: get GURPS Mysteries.
When you are GMing, don’t run puzzle stories. Like hard SF idea stories, they work okay when the writer can reveal the solution to to the readers/audience, but are very unreliable when people who are not in of the trick have to figure it out for the story to work. What you ought to do instead is to run an adventure story with a mystery as the McGuffin. Like a Sherlock Holmes story.
When you are playing, remember that this is nothing at all like reading an Agatha Christie. You can’t wait passively for the clues to march past and then think out the adventure. Your character has to do stuff, or there will be no story. You always have to go places and talk to people to find the clues. Sometimes the clue doesn’t exist and you have to force or trick the villain into doing something revealing. In any case, this is an adventure story, not a puzzle story. You have to go places and do things to get involved in conflict. So for the Dog’s sake, don’t faff around in some vaguely-specified private space arguing about how little can be deduced from the clues. Go somewhere specific, and do something that will get you more information. If you can’t solve the puzzle, get more bloody information!
The biggest obstacle to successful mystery adventures in RPGs is players who try to solve the mystery with the information they’ve got.