Tempting fate / Jane Green.

Enhanced descriptions from Syndetics:

From Jane Green, the New York Times bestselling author of such beloved novels as Jemima J , The Beach House , Another Piece of My Heart , comes an enthralling and emotional story about how much we really understand the temptations that can threaten even the most idyllic of relationships….

Gabby and Elliott have been happily married for eighteen years. They have two teenaged daughters. They have built a life together. Forty-three year old Gabby is the last person to have an affair. She can't relate to the way her friends desperately try to cling to the beauty and allure of their younger years…And yet, she too knows her youth is quickly slipping away. She could never imagine how good it would feel to have a handsome younger man show interest in her--until the night it happens. Matt makes Gabby feel sparkling, fascinating, alive --something she hasn't felt in years. What begins as a long-distance friendship soon develops into an emotional affair as Gabby discovers her limits and boundaries are not where she expects them to be. Intoxicated, Gabby has no choice but to step ever deeper into the allure of attraction and attention, never foreseeing the life-changing consequences that lie ahead. If she makes one wrong move she could lose everything--and find out what really matters most.

A heartfelt and complex story, Tempting Fate will have readers gripped until they reach the very last page, and thinking about the characters long after they put the book down.