I play it from time to time, it's no Toca Race Driver 3 but there's quite a lot of content there to keep you busy.
Graphically it's not mind blowing and certainly won't push your graphics card very much even at 4K resolution I only get about 60% GPU usage.
Physics are sort of somewhere between Grid 2 and F1 2013.
At that price I'd say go for it, the DLC isn't essential to the career mode but does add some cool additional events as well as bringing back some older tracks from grid 1 and 2.