Who is Boaz Katznelson from The Things a Brother Knows and what is their importance?

Boaz Katznelson lives in a small community outside Boston, Massachusetts, with his parents and younger brother, Levi. As the story opens, Boaz is due home after having been away for three years. He had joined the US Marine Corps right out of high school and spent several tours overseas in the battlefield. When he returns home, he is greeted as a hero but he feels anything but heroic. He is uncommunicative and remote. He spends all of his days locked in his bedroom. He will barely talk to anyone and will answer no questions about his experiences or what his plans are.

But Boaz has big plans. He downloads maps of the Northeastern US and has old maps hung all over his wall. He has penciled in some notes and addresses on his maps. He tells his family that he is going to hike on the Appalachian Trail during the summer but his younger brother, Levi, knows better. He's seen all the maps and he hacked into his brother's email account. He has evidence that Levi is not going to the Appalachian Trail; rather, he is heading for Washington, D.C.

Much to his brother's dismay, Levi figures out the direction in which Boaz is heading and joins him on the hike. Boaz refuses to tell his brother where they're going or what his mission is—only that he must complete it. In the end, Levi learns that his brother had some horrific experiences in the war. His best friend lost both legs and Boaz himself is suffering from PTSD from his wartime experience. He is filled with guilt because he, along with fellow marines in his unit, shot into a van that was racing toward them. Their fire killed three young teenage boys - boys close to Levi's age at the time. The guilt has haunted him ever since. After Boaz pays tributes to all victims of wars at the Vietnam Memorial in Washington, D.C., he is ready to get the psychological help he knows he needs.