The God Machine by Ken Newman

In 2014, nineteen-year-old budding novelist, Kieran Nash, finds himself inexplicably transported to the desert world of Adeaa, where he meets an equally bewildered squad of German paratroopers, plucked from a 1944 Italian battlefield. Putting differences aside for the sake of survival, Kieran and the war-hardened German Fallschirmjäger—led by the ever-resourceful Captain Zimmer—set out across the dangerous new world to find a way home, unaware they are key players in a plan that affects the future of two worlds.