I have no intention of spoiling this book for anyone. If you have enjoyed following the trials and travails of October Daye from the beginning, then you should read this book. If, however, you have not, then you should start with Rosemary and Rue.
That's because this book (like the two before it) is immensely satisfying for existing readers, furthering the story while illuminating previously unknown parts of the world McGuire has built. However, it also mentions, builds on, or otherwise includes elements from previous books. While Toby does her best to signpost them in her narration (the book is told in first person), enough to remind loyal readers, I'm not sure that a complete newbie would get as much out of it.
A complication of Faerie Law makes it imperative for Toby to find and restore Simon Torquill, the Fae noble who turned her into a fish before the start of the first book ... and who also happens to be the father of her half-sister, and who is currently half out of his mind and at large as the result of ... see, even attempting to summarise the main plot driver is complicated. Suffice to say she has to find him in order to get married, and sets off on a quest that rapidly becomes far more than she had planned for.
But ignore my poor précis, and instead read this book because it has all the things that make this series so beloved: sparkling dialogue, complex plotting, multi-layered characterisation, and clever writing.
I enjoy any chance to spend time with Toby and her coterie of friends and acquaintances, despite her tendency to bleed on everything ... and this latest book in the series is no exception.