Firefly Lane by Kristin Hannah

Britt's take

This book captures what it feels like to have a friendship that is an entire era of your life. Tully and Kate meet at 14 and spend 30 years being the person the other one can't function without. The book follows their friendship through marriages, careers, motherhood, resentment, and the specific grief of watching someone you love become someone you don't recognize. It's nostalgic, emotional, and heartbreaking, but centered on the comfort of having someone who has known every version of you. It's not a traditional happy ending. Prepare yourself.