Faking It Next Door (Cedar Vale Chronicles #1) by Sinclair Kelly

Summary (spoiler-free):
Annika returns to the small town of Cedar Vale to help manage her grandmother's beloved bookstore after a difficult breakup. Wanting to avoid the attention of her persistent ex-boyfriend and the town's gossip mill, she finds herself in a fake-dating arrangement with her next-door neighbor—her former high-school rival—and his two best friends.

What begins as a simple plan to keep her ex at bay quickly becomes complicated as real feelings develop. Living in close proximity, running into each other daily, and maintaining the charade forces Annika to confront old grudges, new attractions, and the possibility that the perfect relationship might not look anything like what she once imagined.