The Fifth Child by Doris Lessing

I was intrigued with this story by a brief random reading in the middle of the book. Reading the whole book left me wondering if this was a horror story, science fiction, or, as the book jacket suggests, a metaphor for our inability to manage the challenging new world order we have created. Amidst the free love era of the 60's a British couple instead chooses to marry and create their utopian vision of a large happy extended family frequently celebrating together in their large comfy house. Until Ben, the fifth child is born. He is strong, angry, intellectually slow and scary in a sense that isn't easy to define. His existence forever alters the family dynamics, ends their happy lives, and gives rise to the suggestion that he is actually something other than human. This is something other than your typical dysfunctional family novel but I am not sure what.