In 'Love the One You're With,' Emily Giffin takes us into the perfectly crafted life of Ellen, who is married to Andy, the ideal partner. Their fairy-tale beginning teeters on the edge when Ellen encounters her past love, Leo, whose reappearance stirs up a whirlwind of forgotten feelings and what-ifs. As Ellen grapples with the remnants of a past heartbreak and the reality of her seemingly flawless marriage, she faces a poignant dilemma: the struggle between the security of the life she has built and the lingering thoughts of a love that never truly faded. This emotionally rich tale navigates the complexities of love, fidelity, and the haunting power of memories, challenging us to ponder the essence of true happiness.