Ancient (Thaumatology, #8)

Ceridwyn Brent has invented a way of creating an artificial ley line and is planning to use it to generate free, clean electricity. To do that, however, she needs to start the line in an area of high magical energy and in Europe that means the German Rift. At the end of World War II, a series of huge explosions in German cities cracked open the world, letting demons and fae run rampant, and that rift line is still a huge area of high magic. So, Ceri and her friend, Lily Carpenter, must walk into what is left of Hamburg to initiate the ley line.
Something is wrong in the ruins of Hamburg, however. Sensitives are having strange dreams of some old evil rising from underground and the shadows seem to move on their own. Something bad has woken up and it seems to be fascinated by Ceri. It also has far more extreme motives and, when it follows Ceri and Lily back to London, blood and chaos are not far behind

I'm a computer programmer who has been writing fantasy and sci-fi since I was fifteen. The Thaumatology series is, therefore, the culmination of 30 years work! Wow! Never thought of it like that.