Divided Serenity by G.L. Cromarty

John Tanis dreams of killing the man responsible for his exile.
Once loyal to the civilized Aterra, John now fights for Shadowland. But the mysterious arrival of technology outside the wall heralds change.
With the dividing wall failing his new loyalties will be tested, and he must choose between revenge and saving the people he once loved
When the ancients colonized the planet named Serenity they displaced an indigenous population and constructed a vast force-field wall to keep the Aterran colonists safe. Eons have passed. The two parts of the world remain isolated: those inside the wall with technology, and those outside the wall with none. The Aterrans have long forgotten their ancient founders wrongdoings and care little for those who live beyond their wall.
Until an earthquake destroys their protective wall—at least that’s the official report.