Fred Robbins is an enigma, even to the person closest to him in the world, his sister Ava.
He might be the purest possible outcome of the experiment that his late parents conducted upon him, bringing him up free of the imposition of adult mores and inhibitions - or he might be autistic, or have Asperger Syndrome, or lie somewhere along that spectrum.
He might be an innocent, and innocent of the crime of which he is accused, or he might be a sociopath. No one really knows.
Fred has been arrested in connection with the death of a 12-year-old boy, Jimmy Ferebee, whose half-naked body has been found in woodlands remote from his home and marked with signs of violence. Fred has been described to the press as a vagrant, living in a flat above a garage belonging to the dead boy's grandparents. It doesn't look good for him.
This is the considered opinion of the elderly, harassed lawyer whom Ava consults before going to visit Fred. While she feels certain her brother did not abuse and murder the boy, the trouble is, she just doesn't know.
No Book But The World purports to be a "confession" written by Ava, reminiscing about her and Fred's unconventional childhood and the most significant episodes in his adult life leading up to the crime. She gathers information from her husband and from her best friend Kitty, both of whom have known Fred and Ava since they were kids.
In their testimony there are hints and clues that seem to align in favour of Fred's guilt: flashes of violence and calculated meanness that seem to belie her preferred image of her brother as gentle and naive; recollections of a sexualised game that she, Kitty and Fred played as adolescents; a telling episode where a family recruited Fred as a companion/babysitter for a boy while they went away on holiday, only to return early with the boy badly injured and Fred implicated.
Leah Hager Cohen's strength is characterisation. Her last notable work, The Grief Of Others, was the portrait of a family, each of the members and the dynamics between them painted with complete precision. She plays to her strength here, too, particularly with the creation of the prickly, baffling character of Fred, on which the novel and its twists all hinge.
And the background is drawn with as much attention to detail as the foreground: Ava and Fred are the children of an ageing educational psychologist, the founder of a "freedom school" whose glory days are past, but whose fascination with the development of young minds free from conventional controls is undiminished and focused on his own children.
The school, Batter Hollow, and its founder, Neel Robbins, were apparently inspired by the real-life examples of England's Summerhill School and its Scottish educator A.S. Neill.
Robbins is an admirer of the French liberal philosopher Jean-Jacques Rousseau, who urged that in growing up children ought to use "no book but the world", experience being the best teacher.
This gives rise to the central question that Hager Cohen poses: how are moral adults produced, by nature or by nurture?
No Book But The World is a brilliantly rendered novel, slow to get under way but intelligent, thought-provoking and capable of some deft narrative footwork, too.
No Book But The World by Leah Hager Cohen (Profile Books $35).