I bought this as a gift on the recommendation of a German colleague. What is it? It is a pack of cards with a riddle on each card, for example "A woman dies because she was on the phone too long. How did it happen?". One person turns the card over and reads the answer (not out loud). The rest of the group ask questions, which can be answered "yes", "no" or "irrelevent" and have to find out the circiumstances of the death. Some are relatively easy, some are extremely lateral. The answer to the question above is that the woman was taking her car home from the garage after having it serviced. The garage were trying to call her on her mobile to warn her there had been a mistake and the brakes hadn't been fixed properly. The woman was too busy on the phone talking to her friend (on hands-free of course) and never took the call or listened to her voice-mail. As a result she wrapped the car around a tree and killed herself.
That riddle kept a group of adults and teenagers occupied for about 30 minutes before they worked out the answer (with a few hints). There are 50 such riddles in the box so the longevity is quite good, even though you can't really re-use the cards with the safe group of friends.
If you're looking for a cerebral party game which is definitely a different to Pictionary or Trivial Pursuit, then I highly recommend this.