So Thirsty by Rachel Harrison

Sloane Parker is dreading her birthday. She doesn’t need a reminder she’s getting older, or that she’s feeling indifferent about her own life. Her husband surprises her with a birthday-weekend getaway―not with him, but with Sloane’s longtime best friend, troublemaker extraordinaire Naomi. Sloane anticipates a weekend of wine tastings and cozy robes and strategic avoidance of issues she’d rather not confront, like her husband’s repeated infidelity.

But when they arrive at their rental cottage, it becomes clear Naomi has something else in mind. She wants Sloane to stop letting things happen to her, for Sloane to really live. So Naomi orchestrates a wild night out with a group of mysterious strangers, only for it to take a horrifying turn that changes Sloane’s and Naomi’s lives literally forever. The friends are forced to come to terms with some pretty eternal consequences in this bloody, seductive novel about how it’s never too late to find satisfaction, even though it might taste different than expected.