An Act of Murder is a classic country-house mystery: an isolated estate, a small group of suspects, a limited amount of time to solve the crime.
The country-house mystery premise has been done numerous times in interactive fiction: consider Infocom's Deadline, or Sierra's Mystery House. Even in the best of these, though, the game-play almost always fails to capture what's essential about detective fiction. Even at their best, mystery IF games usually test the player's thoroughness (have you looked under every bed? analyzed every object?) and patience in replaying (have you tried spying on all the characters at all the available times of day?), rather than his logical thinking and deductive abilities.
An Act of Murder stands out because it does ask the player to focus on drawing conclusions: what do you know? What do you need to find out next? What do these alibis mean? There are a few objects to discover, a few pieces of evidence that have to be searched for, but for the most part, Act of Murder is about the conclusions you draw, and how you figure out where to look next.
