Watermelon by Marian Keyes
Claire has everything she ever wanted: a husband she adores, a great apartment, a good job. Then, on the day she gives birth to her first baby, James tells her that he's having an affair. Claire is left with a beautiful newborn daughter, a broken heart, and a body that she can hardly bear to look at. So, in the absence of any better offers, she decides to go home to her family in Dublin. Sheltered by the love of her quirky family, and the attention of an incredibly attractive younger man, Claire gets better. A lot better. In fact, so much better that when James slithers back into her life, he's in for a surprise.