The Fifth Letter

I enjoyed The Fifth Letter by Nicola Moriarty, which is set in Sydney, Australia.  Four women, now in their 30s, meet for a holiday in a house near the beach.  They have been "besties" since they started high school.  One of them suggests they anonymously share a deep secret and they do so by using an old working computer and printer in the house.  They resolve to open one letter each night.  However, a fifth letter is discovered which will have a powerful impact.  I disliked the characters but there was enough mystery towards the end as we finally learn who wrote the fifth letter and the reason for writing it. 4/5