This is the best of the solo rpg systems. It is quite simple to grasp and is quite robust in handling multiple adventures. The flexibility of the rooms means that the graph paper gets filled in a balanced and believable way. The ability to level up and go on an over-arching campaign that embraces multiple adventures, makes this compelling. The pocket forms of the rules and tables means it is perfect for long train journeys!
When we consider how the system has so many expansions and published adventures, this is a winner.