This Used to Be Us by Renée Carlino

There are two sides to every love story—and every breakup. Get ready for an emotional roller coaster of family, marriage, and divorce that will have you both laughing and crying, from the bestselling author of Before We Were Strangers.

After twenty-two years together, Danielle and Alex are getting a divorce. Once fiercely in love, they can barely stand the sound of each other’s voice. Instead of shuttling the kids between two broken homes, Alex and Dani decide to share a nesting apartment while swapping days with their two teenage boys at the family home.
In the apartment, Dani and Alex, on their own, begin to reflect on the last two decades—why they fell in love and why the marriage fell, spectacularly, apart. With the newfound space and time, they are given a chance to rediscover their autonomous selves again. They both get back in the dating pool. Dani finds major success at work as a showrunner on her own TV project, while Alex faces the challenges of a new relationship.
Still, they find that they just can’t stay away from each other, and somehow, the distance allows them to remember (for the first time in years) what each used to love about the other. When a family crisis draws them back into each other’s orbit, Dani and Alex are once again put to the test, which leads to a dramatic conclusion that will have readers weeping.