The story is set partially in the contemporary world of England and partially in the world of Lyndesfarne. In Lyndesfarne, all but the simplest technology does not work, but a sophisticated society functions using pervasive magic. The crossing between the worlds is formed by two stone causeways across the marshes, joined by the Old Bridge; its immense masonry arches are partially reinforced by steel alloys and by magical sprites, visible as orange sparks inside the stonework itself. A short section in the middle of the central arch, in the region where neither engineering nor magic is entirely reliable, requires both metal and magical enhancement ...
An alphabetical glossary of terms and an index of characters for the world of Lyndesfarne is available on the author's website: http://www.lyndesfarne.org/glossary.html
Also by Trevor Hokins on obooko:
Death on the New Bridge
Bridge at War
Bridge of Stone and Magic
Findo Gask: Goblin Detective
Findo Gask: Gumshoe Glamours