There is definitely a pattern to these books.
Toby enjoys a brief respite from whatever it was she had to deal with in the previous book, before all hell breaks loose and she has to do her knight errant thing.
Someone dies, one of her close friends is badly hurt, there is a lot of blood (mainly Toby's) and everything works out OK in the end, usually thanks to the Luidaeg and a deus ex machina. (McGuire actually has the Luidaeg admitting to this).
But for all that, these books are ridiculously good fun and thanks to McGuire's writing I really care about the characters. Especially Dianda, I love the idea of a kick-ass mermaid.