I went into this wanting to love it, but unfortunately as much as I initially liked the epistolary format I found as the novel went on that it just didn't work for this genre - and not just that it didn't work, but that it actively detracted from the book. My favourite parts of detective/mystery novels lie in seeing the investigation, watching the investigator track down leads and try to find witnesses, and getting a look inside their head as they do it. This format strips all of that away, leaving us with the results of investigations (interviews, email chains, diaries, etc) without ever showing us what it took to get there. As a result I never really got a feel for who the main character was, despite spending so much time with her, and I never really cared about the outcome of her investigation.