A child needs your love most when he deserves it least.
Erma Bombeck (1927-1996) was a newspaper columnist and humorist who published books with titles like If Life is a Bowl of Cherries, What Am I Doing in the Pits? (1978) and A Marriage Made in Heaven ... or Too Tired For an Affair (1993). What is a quote from this woman doing in this book?
Well, there is a bit of sincerity to the quote's purpose here. The quote applies to all stages of Kevin's life. Eva never seems to love him, perhaps partly because he never shows her he deserves it. At the end, she seems to start loving her son, even though he still remains remorseless after committing a mass murder. If there is anyone less deserving of love, we don't know who it is.
But the quote from Erma Bombeck, a woman no hipster will ever quote, is also a bit tongue-in-cheek. This is the kind of blanket parenting advice that Eva would roll her eyes at, even if maybe she should be taking the advice at face value. But really, what on earth could Erma Bombeck say about a kid like Kevin that wouldn't be ridiculous? Including the quote as the epigraph shows us some of the book's humor, which is so dark it can be hard to see sometimes.