The summerhouse - Jude Deveraux

'Have you ever wanted to rewrite your past?'
Three best friends, all with the same birthday, are about to turn forty. They plan to share this momentous occasion together at a summerhouse in Maine, talking up a storm and taking stock of their lives and loves, their wishes and choices. But none of them expects the gift that awaits them at the summerhouse: the chance for each of them to turn their 'what-might-have-beens' into reality.
Leslie, Madison and Ellie met nineteen years ago, in the most unlikely of places: stuck in line at the New York City Department of Motor Vehicles. From that memorable day, the day they each turned twenty-one, they quickly grew into an intimate trio of friends. Now, as they reunite on their fortieth birthdays, they each find a puzzling card from a 'Madame Zoya' offering them the chance of a lifetime: to relive any three months from the past...