The Transall saga

Find yourself in another world in The Transall Saga, the latest adventure from Gary Paulsen: Mark's solo camping trip to the desert begins as any other camping trip, until a mysterious beam of light appears.  The trip turns into a terrifying and thrilling adventure when the light beam transports Mark into another time, and what appears to be another planet!  Although he is searching for his way back to earth, in the meantime he is forced to make a life in this unknown world.  He meets primitive tribes and shares the joy of human bonds, but this end of isolation in the new world also brings war and a struggle for power.