Kell is a magician-but a special kind of old-who has the ability through blood magic to cross the dimensions in to the different worlds, each of which has a London. Raised in Red London with his prince brother Rhy, Kell is a messenger, taking letters from the Red Royalty to those of other Londons. In Grey London-boring, magicless London-Kell runs in to his enemies as well as Lila, a thief, and must dispose of an object that has brought a whole different type of magic to the fore. 
 The premise of A Darker Shade of Magic is interesting. It is not wholly unique, but it is intriguing and has elements of being something that had extreme potential, but unfortunately the severe lack of plot, the abysmal world-building and the utterly annoying characters really let it down. 
 The four Londons-and I expect there are more-was the most wonderful thing about this book (and, sadly, the only thing). This is a wonderful concept, but it was never explored fully. I acknowledge this book is the first in a series, but we barely scratched the surface of any of these worlds in a 400-page long book. In a 400-page long book I expect there to be many travels and many subplots when put in the hand of a good writer. This book had one plot and one world, it just so happens it was called different worlds. 
 The writing wasn't particularly bad (though I have no idea why anyone thinks adding extra information within parentheses is a good idea?) but it never truly captivated me. I was never drawn in, my attention was never wholly held. It was good, it was more competent than a lot of authors out there, but it was nothing special. It was simply adequate. 
 My main gripe would be the world-building (or total lack thereof), but similarly and coming a very close second were the characters. Under-developed, obvious and annoying are only three words to describe them. Kell was the most developed, but even then he was rather obvious at times, though some of his decisions were conveyed well. I cannot bring myself to write about the pathetic character of Lila, who I hope dies horribly at some point in the series. The other characters-though billed at main-were background at best. We got no sense of any of them, except perhaps Rhy but even then he was under-developed. 
 For a 400-page book, there needs to be more than just a stupid plot about a magic stone. There are no subplots, no subterfuge, no otherness about it. There was nothing at all, except a short story that was stretched out and stuffed full of padding to satisfy a word count.