Nightbirds follows the story of three “sisters” - Æsa, Sayer, and Mathilde - as they discover the depth of their magic. Set in a sort of Prohibition/1920s era, magic is largely banned and seen as unholy by a religious sect. Ultimately, this book is about the power of sisterhood, of women banding together in a heavily misogynistic society. 

I do like that all four ladies ended up taking a different route towards the end. How they get back together is hopefully something that’s solved in the sequel.