Finally, like a lot of Auster protagonists, Walker is shadowed by a traumatic loss -- a younger brother accidentally drowned as a child.
So far, so Austerian. Invisible throws us a curve, however, in its attention to justice.
Walker recalls (in a section of the novel using second-person narration) that "hours after your mother was carted off to the mental hospital, you swore an oath on your brother's memory to be a good person for the rest of your life." Events he witnessed and participated in during his twentieth year, in 1967, lead him to devote himself to "twenty-seven years of legal aid work, community activism in the black neighborhoods of Oakland and Berkeley, rent strikes, class action suits against various corporations, police brutality cases, the list goes on."
In 1967, Walker was a witness when Born, a man who seemed prepared to help Walker achieve his wildest ambitions, murdered a perfect stranger on a New York street. As the consequences of that moment unfold over the rest of the novel, as we click from first-person narration to second-person and then to third (as Freeman takes control of his friend's story) we recurringly have occasion to ask what being a good person means, what justice requires, what one can and cannot do and still be "good," what the pursuit of justice does and does not permit.
Obviously, this is a Guantanamo-era novel, but these questions are much, much older than that -- just think of Welles's Touch of Evil, to say nothing of the Oresteia.
And the title? As both the plot-starting murder and the final episode (narrated by yet another character, Cécile Juin) of a concealed but suddenly-visible prison colony suggest, justice and injustice have everything to do with what we see, or don't see, or refuse to see.
On second thought, we might say there was an earlier Auster novel preoccupied with justice -- Leviathan. My favorite, as it happens.