Which book is this?

The enemy (2004) · Lee Child Like Enemies (1986) · Sophie Weston Ego is the Enemy (2016) · Ryan Holiday Irresistible Enemy (1990) · Lilian Peake The Enemy (The Enemy #1) (2009) · Charles Higson The Eternal Enemy (1993) · Christopher Pike They Called Us Enemy (2019) · George Takei, Justin Eisinger, Steven Scott When Enemies Marry... (1995) · Lindsay Armstrong Dear Enemy (1915) · Jean Webster Love's Duel (1982) · Carole Mortimer