Back in the Old West, an organisation called the Pony Express carried mail through the badlands from community to community. Now in post-apocalyptic times a similar group called the Postal Riders offer the same service - and the party gets asked to help out in the delivery of some 'holy books' in the face of cultist predations.
It's a straightforward road trip adventure with a few running battles and chase scenes, yet it comes over fresh and new with the wealth of detail provided to bring the whole thing to life. For a start, the party has to navigate through wild terrain, even choose the best route. From then on there are ambushes and challenges galore, with each being laid out clearly with just about every option covered, making it easy to run.
There's a completely off-the-wall episode during the journey, harking back to old cartoons. If you are happy with a 'Looney Tunes' element to your game it works well, but needs to be included even if you prefer a more serious approach as it does turn out to provide useful information regarding the party's mission. Perhaps it's just that the post-apocalypic desert sun has turned a cartoon fan so mad that he's been recreating the stories he no longer recalls as cartoons.
The climax contains a real sting in the tail and is very open-ended - so much so that a full SIX conclusions are provided so that you can run the one most appropriate to the party's actions!
Designed as a 'shared campaign' adventure which could run in a convention slot, it also would fit in well with your own campaign provided you can engineer some reason for the party to be in Reno, where the action starts. Once they are there, let the fun begin!