What drives Coach Belichick? No telling.

IT is America’s most popular, and paradoxical, spectator sport. The average National Football League game is seen by more people on television than the combined audience for an average professional baseball and basketball game, yet most NFL fans have little knowledge of what is really going on.

The intricacies of the playbooks are such that, when a team scores a touchdown, it is difficult to know who is really responsible, and when a team allows a touchdown, it is impossible to place exact blame. We cheer for players whose faces are hidden under helmets. We attempt to understand plays devised in huddles or on headphones. Jim Mora, who coached the New Orleans Saints from 1986 to 1996, once grew angry at a group of reporters attempting to second-guess his play selection, telling them: “You don’t understand the game. You will never understand the game. You don’t see the same things we do.”

Nowhere is the unknown more unnerving than in the persona of one of the game’s greatest coaches, the New England Patriots’ Bill Belichick. His teams have won three of the last four NFL championships, yet we’ve never seen him smile. He is known as the smartest man in football, yet we’ve rarely heard him share. Even walking the sidelines in front of millions of viewers on a Sunday afternoon, he is a portrait of secrecy, his body buried beneath a baggy gray sweatshirt, his face an unchanging bit of rock. Tackling the soul of Belichick, then, is like tackling the legs of his star running back, Corey Dillon. At best, you will be left with bruises; at worst, you will be left with nothing.

So at least give David Halberstam points for trying. Taking his first look at pro football, the acclaimed author examines the inner workings of Belichick in “The Education of a Coach.” What Halberstam did for pro basketball in “The Breaks of the Game” and for major league baseball in “Summer of ‘49,” he attempts to re-create here, delving into the seemingly impenetrable world of a coach who never lets us see him sweat. It is a difficult task, turning a lump of gray flannel and a handful of Super Bowl rings into a human being, turning Xs and O’s into whys. Halberstam attacks it with the grace and confidence of a veteran quarterback, interviewing former coaches and players, tracing Belichick’s life story from the nerdy son of a legendary assistant college football coach to the NFL guru who hugged his dad on the sideline after his three Super Bowl victories.

But this is a Hail Mary pass that doesn’t connect. Belichick grants Halberstam “marathon interviews,” according to the acknowledgments, but apparently never lets Halberstam set foot inside his office, which is described only by a Patriot assistant coach. Belichick allows his friends and colleagues to speak to Halberstam -- breaking his rule that his assistants cannot speak to the media -- but his colleagues speak in guarded generalities or cliches, rarely offering any sort of insight that could not be gleaned from those countless “Inside Football” television shows. In one interview, former co-worker Maxie Baughan says of Belichick, “He understood that the key to success, the secret to it, was the mastery of the grunt work, all the little details.” That might make for championship football teams but doesn’t make for riveting books.

The story begins in 1957, with Navy assistant coach Steve Belichick (who died last week) masterminding a victory in the annual rivalry game against Army, cheered by his 5-year-old son, Bill. The story then spins forward to last winter, father and son being doused in Gatorade on the sidelines of the Super Bowl after Bill’s third world championship in four years. The journey between those two points fills the remaining pages in textbook fashion, a work as complicated and only erratically as exciting as the Patriot offense.

We learn that, as a teenager, Bill Belichick was the recipient of the team’s final game plan on Friday nights before every Navy game, allowed to act as a young advisor, as long as his homework was finished. He is clearly his father’s son. Yet we never learn of any further interaction beyond the sidelines. One of Belichick’s trademarks as a head coach is refusing to allow his players to be personally introduced before Super Bowl games -- each time, the Patriots shunned the television directions and simply ran on to the field as a symbolic unit. We learn that this trait was instilled in Belichick during his years as a small but tough lineman at Annapolis High, under a coach named Al Laramore, who never allowed his teams to wear uniforms with their names. “In the Laramore system, the coach was king, and had been king in the past, and was going to be king in the future,” Belichick said, explaining how the tone was set for his own taskmaster career. The book cites several other Belichick role models, but we are left wondering how exactly he carries their message forward. If there are compelling one-on-one encounters with players, we rarely see them. If Belichick ever raises his voice, we rarely hear it.

There is a bit of magic in the story of Belichick’s first coaching job, working as go-fer for the Baltimore Colts after graduation from Wesleyan. “Look, you don’t have to pay me, but give me something real,” he pleaded with Colts coach Ted Marchibroda. Yes, the high-powered NFL figure once worked free. And later, as an assistant coach with the New York Giants, there is meaty stuff about his relationship with Coach Bill Parcells, a mentor who helped define his career. “If Bill Parcells’ strength came from being the coach who believed that everyone had a button to push ... then Bill Belichick’s strength was to be the coach as the ultimate rational man,” writes Halberstam. But other than the usual ribbing and sideline second-guessing, there are too few examples of their disagreements or lives off the field. In the end, one is left wondering if a book about the button-pushing coach wouldn’t have been a more interesting read.

Belichick’s first head coaching job, with the Cleveland Browns, was one of the messiest tenures in NFL coaching history, as he presided over the firing of star quarterback Bernie Kosar and watched as the team was moved to Baltimore. Yet there is little new here, Belichick admitting to no mistakes and later saying that his lasting Cleveland lesson was thus: “Not to move your team to another city in the middle of the season.”

Football die-hards will love what is the book’s highlight: a breakdown of each of Belichick’s three Super Bowl victories with the Patriots. Halberstam writes of the scheme that stopped the St. Louis Rams’ historic offense, of Belichick’s admitted roster mistakes in the near-loss against the underdog Carolina Panthers and, most poignantly, of his shock during the final minutes of last season’s Super Bowl win over the Philadelphia Eagles. The Patriots were leading by 10, but the Eagles were moving slowly down the field as if they, instead, were leading. “Have I got the score right?” Belichick said into his headset, talking to assistant coaches in the press box. “Then what the hell are they trying to do?” It is a priceless bit of dialogue, the sort of which this book is in painfully short supply.

There are three words that serve as a mantra for anyone daring to explain today’s NFL to the masses who truly don’t understand. Make it human. While Halberstam makes Belichick interesting and occasionally compelling, he does not make him human. When Belichick’s separation from his wife is noted in the final pages, it is a shocker mostly because there is scant previous mention of a wife, or his three children. We rarely see Belichick at home, or in the office, or anywhere but in the playbooks that have defined his legacy team. This is, one supposes, a book that Bill Belichick would have loved to have written. Not surprisingly, that makes it ultimately unsatisfying to read.