This DLC is a standalone story that doesn't tie into the events of the main game in any meaningful way, which is fine. (pcgamer.com)
While I appreciate the new levels, why weren't they part of the main game world? (pressthebuttons.com)
That is to say, it's not terribly deep, but it is a lot of fun, and there are tons of racing challenges to play through outside of the main game. (xboxexclusive.com)