The Fifth Letter by Nicola Moriarty
My love of Australian authors Jaclyn Moriarty and her sister Liane Moriarty has been pretty well documented here on VBPL Recommends (see Feeling Sorry for Celia, A Corner of White, Big Little Lies) and I was aware that their younger sister, Nicola was also a published author, but unfortunately her novels had only even published in Australia, until now...
The Fifth Letter, Nicola Moriarty's US debut, tells the story of a group of female friends -- now in their thirties, who have been friends since high school. Joni has always felt like the organizer in the group, and now worries that they're drifting apart, as all of her friends are busy with their husbands and children. On an annual girls' weekend, she comes up with an idea to bring them closer again, to each share one secret in an anonymous letter.
Each of the four women heads down to the basement bedroom to write their letter in turn, but one of them has second thoughts during the night and sneaks back down to write a new letter, replacing her original and intending to destroy it. But Joni finds this "fifth" letter and the secret contained within may be devastating, or even dangerous, to the friendship of the group.
Moriarty takes the reader back and forth in time, switching between the annual vacation, Joni's confessions to a young priest, their high school days, and very short snippets of the fifth letter. In this way, her writing is very reminiscent of her sisters', with well-differentiated female characters, epistolary elements, and a slow, careful plot reveal.
For readers who enjoy The Fifth Letter, I would definitely recommend the novels of both Liane Moriarty and Jaclyn Moriarty (keeping in mind that the later are mostly YA), along with the adult novels of Rainbow Rowell, Attachments and Landline.