I loved the Iron Druid series, but was a bit hesitant about this one because I grew up in Glasgow, and I was worried that an American writing about my home city would just be too jarring. Happily it really works, I can see Al McBhairrais as a proper weegie. There are a few bits that didn't quite match, but I can see that as being to help the US audience, like talking about autos, and paying your tab on the way out of the bar.
Ink & Sigil is the first in a series, and it does a lot of work in setting the scene and establishing the characters and their supporting cast. The plot isn't that heavy, and Al isn't really a detective, although he does hunt down the Fae that have made unauthorised trips to the mortal plane. Al's one of six sigil agents, all mortal humans, that enforce the pacts between the gods not to interfere on Earth. The sigils, drawn with special inks, give them the edge they need to get by without notice, and to deal with the treaty breakers.
The Glasgow that Al frequents is one I recognise, even though I've not live there for over fifteen years. I guess a bit of research (Kevin Hearne spent a few weeks in Glasgow before he wrote this) and Google maps make it easier to write about places you don't know intimately.
I really enjoyed the backstory to Al, and how he met his manager Nadia, a Scots battle seer of Indian descent. She's a very real seeming character, and I could imagine meeting her in real life. There's also more added to the Iron Druid universe, looking at it from a new perspective. So I'm looking forward to the next installment, which is due out later this year.