Oh the speed...!
There are a large number of tracks which you unlock as you go, though most of them are variations of several basic models. They are different enough, fortunately, to remain interesting and challenging. I found it fairly easy much of the way to place first all the time (with some pre-race practice), but near the end, the difficulty ramped up pretty quickly and I started finding my opponents on my heels or zooming ahead all the time. The very speed with which turns and obstacles hit you forces you to be on your toes all the time if you want to make a near-perfect run (which is crucial in the most difficult races). So racing in this game takes a good deal of concentration and reflexes, but my, is it exciting. One learns, after a while, when is the best time to boost the engines (which really makes a difference) and how to take less damage after going airborne. The upgrading aspect is also cool, and it's satisfying to see the specs on my pod go zooming up every time I win some prize money and go shopping.
Overall: fun and exciting racing action, definitely worth a try!