Good stuff - fun world-building throughout with the multiple Londons divided by magic and colour.
I enjoyed Kell and Delilah's interplay and it was interesting to see that she seemed to have a bigger character arc ahead of her than the MC, Kell. (Which is in no way a bad thing either.)
Smooth writing and some great minor characters in there too. If I'd wished for one thing from 'A Darker Shade...' it would have been a little more time spent with the villains.
But I'll still be grabbing book 2, that's for sure.