Buzz Bissinger has two extraordinary sons. Gerry and Zack are twins, born three minutes apart and 13 1/2 weeks prematurely. At birth, Zack weighed 3 ounces less than his brother and, because his lungs were less able to carry oxygen to his brain, he was born, in Bissinger's words, "mentally retarded," while Gerry was born normal. Twenty-four years later, the high-functioning Gerry attends graduate school; Zack bags groceries.

Bissinger describes Zack as a savant, having "an unlimited hard drive that saved every answer. I saw these give-and-takes as tiny ships of hope on the darkened sea, beacons of promise that would one day spread over the water until you could see the shore. He would make it to the island of normalcy, even though there is no such thing."

During one of these moments of hope, Bissinger dreams up the idea of taking Zack on a father-son, cross-country road trip (Philadelphia to Los Angeles) in which they might move into new emotional territory that would bring them closer than ever before.

Yet Bissinger has doubts about his own motives. Before they leave, he suggests that this might be nothing more than a father filled with more than the usual share of middle-age guilt, "forcing his imprint on his son and creating an experience that only becomes memorable because both parties spend a lifetime unsuccessfully trying to forget it."

So goes the story line for this bruising yet tender memoir, "Father's Day." Zack and Buzz move through their past lives in Chicago, Milwaukee and, later, Odessa, Texas, the scene of Pulitzer Prize-winning Bissinger's most commercial success, "Friday Night Lights."

The memories are bittersweet and the conversations one-sided, almost forced. Bissinger wants epiphanies. Zack wants to study his beloved maps. Bissinger is impatient. Zack is a Buddha of calm. In Milwaukee, they stop in front of an elementary school, where, as a boy, Zack sadly received no special attention for his needs. Bissinger says, "You were lost."

"What do you mean I was lost?"

"You were having a lot of trouble keeping up."

"I couldn't keep up with things?"

"Do you know why?"

"I couldn't really figure out what I was doing?"

"Do you know why that is?"

"Because I wasn't born great that might have been it."

There are moments in this journey when you wish Bissinger would get out of the way, would stop beating himself up over former marriages and career failures, and keep the focus on the trip. Because when all the regrets fade into the background, we are left with a father who loves his extraordinary son more than he loves himself.

"He is not the child I wanted. But he is no longer a child anyway. He is a man, the most fearless I have ever known."

Stephen J. Lyons is the author of three books, including "Landscape of the Heart," a memoir about his years as a single parent.