From the introduction:
Transposed D&D tropes go fight monsters in the desert at night using monster trucks.
Elves, dwarves, humans, and some dragonborn live in a small desert town (think Nevada). The town is rural and remote. Almost all of its inhabitants are obsessed with Monster Truck derbies, and everyone and their dog seems to have a monster truck. You run a monster truck repair shop you bought after the original owner went missing.
The town's economy is dependent on tourists coming to see the derby, which is where you guys come in. On top of your mechanic duties you also take it upon yourselves to maintain the town’s good reputation by keeping it safe from ogres, orcs, and other monsters. Since you spent all your money on getting the shop set up, you can't afford your own vehicles, so you secretly have to use the trucks in the shop. Don’t wreck them!
Their owners will expect them by morning!