Lisa Jewell 
Thirtynothing 

The hit romance about the havoc an old flame can create, from the bestselling author of I Found You and Then She Was Gone
This blast from the past will knock them off their feet . . .
Dig Ryan hasn»t seen Delilah for twelve years, but when she bursts back into his life he can»t help falling for his first love all over again.
Nadine has been in love with Dig for fifteen years, so she can»t help feeling cheated when her best friend has his head turned again by her old nemesis Delilah.
But how low will Nadine stoop in order to make Delilah go away?
And how can she make Dig realize who he really loves?
»Will keep you up all night in a sweaty, addicted reading frenzy» The Times
»Very entertaining and very funny» Heat
»Jewell writes with invigorating zest and lashings of emotional intelligence» Independent
»Wary, funny, realistic and immensely readable» Cosmopolitan