I'm giving this top marks for an UF for several reasons. 
 1. Plain enjoyment! (This one should be obvious but it doesn't always work even with a lot of other titles I respect across the board. I may love bits and pieces of them, but then you come across writing that is a breeze to fall into and enjoy throughout, and then you know you've got a real winner on your hands. That's this one.) 
 2. Geeky, rather a loser London Police Constable with a bit of a new magical talent, a heavy steeping of modern sf/f culture, and an even heavier steeping of police procedural and depth of characterization. It feels real and I just love this guy. 
 3. It's not light on the Londonite scene! This is great grounding and full of great humor and history, bringing in some of the weirdest tidbits of the past centuries like the proverbial grab-bag and shaking it about a bit and giving us a hell of a weird novel. It's a total blast. 
 Any one of these reasons should have been enough, but damn... who cares! It's a great read! Some of the best UF created, in fact. I can't wait to delve into the rest!