(Yes, I know I'm behind... I wasn't online this weekend :P)
Even setting aside the word "conjured," there was really only one choice for this one.
Kate Griffin's Matthew Swift/Urban Magic series is built upon one key rule:
"Life is magic."
Given this rule, the teeming metropolis of London, with its rushing trains and busy streets, its graffitied walls and glass skyscrapers, its ancient walls built upon its bones in layers of history written upon brick and stone... well, London must be fairly drenched in magic.
Kate Griffin's world combines a whimsical creativity with a wholehearted love of her city. She paints a vibrant portrait of a London where wendigos and fae walk the streets, yet rather than lose the essence of the city, the supernatural embellishments serve to amplify the true soul of the city. Griffin's delight and wonder in the life of the city makes the magic of her world nearly tangible. Her lush stream-of-consciousness style may be a turnoff for some readers, but I think it only enhances the world that she creates. From golems made of trash to imps who colonize vacuum cleaner bags to electric druids who live inside the city's lamp-posts, Griffin creates a world that is extraordinary and eccentric, a world that is rooted in a a tangible affection for the city.
I reviewed the whole series about a year ago, starting here.