The bone house - Stephen R. Lawhead

Kit Livingstone has been bequeathed by his great grandfather, Cosimo, an apparently impossible task: to piece together a 17th-century map whose fragments are scattered not just throughout this universe but other universes too. One piece of the skin map has been found. Now the race to unravel the future of the future turns deadly. Aided by his girlfriend, Mina, from her outpost in seventeenth-century Prague, Kit begins to make progress but realises that opponents, in the shape of the Burley Men, are equally determined to capture the map, and they have a crucial advantage: the ability to manipulate the will of historical figures for their own ends. Across time and space, through manifest and hidden worlds, those who know how to use ley lines to travel through astral planes have left their own world behind in this, the second quest: to unlock the mystery of The Bone House.