The Shadow Year by Hannah Richell; published 2013 by Grand Central Publishing
Opening line: “Lila sits at one end of a deserted picnic bench with a cup of coffee before her.”
In the 80s, a group of college friends decide to try living together commune-style in an abandoned cottage for a year, with no electricity, limited groceries, and no outside contact. Their leader, Simon, is charismatic, moody, and unstable—and Kat is utterly in love with him. Things are going pretty well at the cottage until Kat’s sister, Freya, discovers them and decides to join the group. Even though Freya insists she doesn’t care for Simon, when it’s discovered that Freya is pregnant with Simon’s child, it is all-out hostility between the sisters. Meanwhile, Simon becomes even more controlling.