The Last Exodus (The Exodus Trilogy) by Paul Tassi

Description

The Earth lies in ruins in the aftermath of an invasion, the land devastated by an intergalactic war where neither side won. The seas are drying up while the atmosphere corrodes and slowly cooks all remaining life on the now desolate rock.

Few survivors remain, but one of them is Lucas, an ordinary man hardened by the last few years after the world's end. He's fought off bandits, murderers, and stranded creatures on his long trek across the country in search of his family. What he finds instead is hope, something thought lost in the world.

There's a ship buried in a crater wall. One of theirs. One that works. To fly it, Lucas must join forces with a traitorous alien scientist and a captured, merciless raider named Asha. Their perilous journey fighting savage men and creatures alike takes them across the remains of the planet and far out into the stars to…where exactly? Lucas has to live long enough to find out.