Here's the premise: A writer of mysteries and a poet who were once a couple long ago but have since split up and are now friends - sort of - decide to write a comic mystery together. They will write alternating chapters of the book and will not collaborate as far as the story line and the characters are concerned. Each writer will respond to what his/her partner has written in the previous chapter and will expand on it and move the story forward. Someone actually thought this was a good idea.
But that's not all! In addition to the book that the two are writing, the emails and notes that each writes to the other, commenting on his/her partner's work, will be included in the book between chapters, providing a sort of book within a book and a running commentary on their writing process. Again, someone thought this was a good idea.
The result of this attempt at cuteness is an incoherent story and characters who are so annoying that I kept hoping that they would all somehow fall into the clutches of the serial killer who seems to be at work here. There is not a single likable character in the whole book, nor very many believable ones either.
As for all those "notes" by the authors, they are petty and unfunny. There is a lot of very unattractive passive-aggression going on here. One suspects that there are many unresolved issues in their relationship, and one could only wish they had found another way to address them - one that didn't involve innocent readers. How about dueling pistols at 20 paces?