We Need to Talk About Kevin by Lionel Shriver

Eva never really wanted to be a mother; certainly not of the boy who murdered seven of his fellow high school students, a cafeteria worker and a teacher who tried to befriend him. Now, two years later, it is time for her to come to terms with Kevin’s horrific rampage in a series of startlingly direct correspondences with her estranged husband. Uneasy with the sacrifices of motherhood, Eva fears that her dislike for her own son may be responsible for driving him so drastically off the rails.