Shuttle is a vastly underrated and undersold simulation, probably because it is a “hard” SCI-FI game with a steep learning curve. This is the perfect game for would-be astronauts. It's a very realistic (and the only decent) simulation of the Space Shuttle. This one should not be approached by casual gamers, as this game is rock-hard. The flight model is very good, and it the glide test, the shuttle really handles like the enormous winged brick it is. Avionics are very detailed, and you should get a proper manual to get to use this game effectively.
The manual accurately describes the launch and mission procedures, and unless you happen to work on the space shuttle program, you'll very likely need it. Graphics are very good for the time, sporting good old polygons. Sound is somewhat limited, but decent.
This is a great game that has never really had a sequel, but one really needs to persist with it. Definitively recommended.