In Odd Spirits, we get to see Moira and Rhys in the early days of their marriage just after their honeymoon period has seemed to lapse and watch as they learn how to communicate with each other and grow together. Despite the brevity of the book, Moria and Rhys feel like complete characters and we see them develop in real time as they deal with their own insecurities and the isolation they feel when they stop talking to each other. 

I truly enjoyed getting a more in depth look at these characters and revisiting the world S.T. Gibson expanded upon in Evocation. Rhys and Moria's relationship in that book is much more mature and seeing how their marriage began helped explain why they were so secure in Evocation. 

I would absolutely recommend this book and think it would work equally well read either before or after Evocation, especially if you want some more time with Rhys and Moira. A wonderful bonus was the beautiful illustrations in this new version. Thank you very much to Angry Robot Books and NetGalley for the advanced copy.