It's difficult to design a true mystery game. Classics like Clue may involve a mystery but they're more about process of elimination than solving a case. Players who want to puzzle over clues and be the first to solve the crime may want to take a look at 221B Baker Street.
221B was written more than thirty years ago. When the game begins you're read an introduction to a mystery case of some sort- it may be a missing person, a burglary, or a murder for example. You are given a list of suspects and relevant locations and facts. Then you set down your playing piece on a map of the city of London. Each turn you roll a die and move your token towards some location. For example, the burglary took place in the post office so you head in that direction. Another player may move towards the park. When you arrive at that location you receive a clue specific to that location. If other players want that clue they're going to need to move to that location as well. When you have enough clues to solve the case you move your token back to the starting square and announce your solution to the case. If you're right, you win.
The game has many features that set it apart from other mystery games. For one, the cases grow progressively more tricky. This is a game best suited for thoughtful teens and adults. If you and your teens enjoy a clever mystery then you'll be very happy with the ones offered in the game. Players will also feel a real sense of urgency and drama as the game goes on. One player gets to "the museum," reads the clue, and smiles. Panic ensues- is there an important clue there? Is the person bluffing? Should you send your token to the museum or send it elsewhere? Some clues are helpful and some aren't. No single clue will solve the case so you will never find a player visiting one spot and immediately winning.
So who would enjoy 221B Baker Street? I personally enjoy trying to solve mysteries and I found 221B to be lots of fun. The cases are just hard enough to make you think but not so hard and obscure that they'll be frustrating. There are also many additional cases available for purchase so the game has a long long playing lifespan. 221B does require the players to pay close attention and think about the clues. Keep that in mind in deciding if it's right for your players.
One other complication about 221B Baker Street is that it may be quite difficult to find. Happily it is available on EBay and seems to be priced very reasonably.
Pros: Exciting and well written mysteries
Lots of additional cases available
Cons: Requires reading and concentration
Out of print so you'll probably find it on EBay
Beyond the Basics: The game has good replay value but it's not something you're going to get better at with additional play. For mystery lovers, however, the 10th game will be just as fun as the first.