You could definitely classify We Need To Talk About Kevin as a Marmite book. You cannot read this and not form an opinion.
It is written as a set of letters from, Eva, the mother of Kevin, to Franklin her husband. In each letter she explains her feelings, fears and concerns over all sorts of things, with Kevin either being the primary focus of the letter or has some relevance to him. The letters are written in chronological order, from pre Kevin days, birth, as a baby, toddler and a small child, and onto the birth of his sister and adolescence, until the incident.
She comes across as a very unnatural mother, and coupled with the fact that Kevin is not a normal child then there is immediate tension between her, her husband and Kevin. I feel that Kevin is a psychopath, partly because he is very controlled in what he does and reveals, he has no empathy with anyone else, be it family, neighbours or friends. His mother I think has some idea of the things that he might be capable of, and raises these concern with Franklin, who dismisses them casually.
I think that Shriver has written the characters that seem normal at first, but then start to grate. The book asks the question when these horrific incidents take place, is it the fault of the i) child, ii) the parents) or iii) society, but she doesn’t answer it and leaves it up to the reader to form their own opinion.
It is very cleverly written, but grim to read.