Rare has made a gem, and if nothing else, this game is quite novel. It was one of the first games to successfully use the multiple-vehicle strategy now popularized by Grand Theft Auto III. One big difference here though is the extreme uniqueness of every vehicle. Each vehicle has certain abilities and qualifications that make it right (or wrong) for the task at hand.
There are a lot of different missions that test different abilities. Missions include rescue, racing, demolition, puzzle solving, exploration, etc. These missions keep the action plentiful, but don't go looking for any in-depth story or meaning behind the game.
One of the major problems is that it is easy to get stuck on a lot of levels. In fact, after all these years, I'm still stuck on certain parts. :P