Wanderlust — Barbara G. Tarn

Rediscover Earth 400 years after the Apocalypse. Daring to boldly go onward without looking back.
Six years passed since Raj and Bel emerged from Rainbow Town and settled in Roanoke when the Wanderlust Bug bites him again. He wants to see what else is left of human civilizations, but mostly where those damn alien disks come from.
With Bel and a few friends, they start a journey through 25th century North America, heading for the Wild West where monsters roam the night.
A cross-country journey in search of more truths about the apocalypse, its survivors and the alien invasion.