You know the outcome of “Long Mile Home,” a new book that reconstructs the Boston Marathon bombing, even before you start reading. Thanks to days of around-the-clock news coverage, the events of a year ago are still fresh in our minds — the two bombs that exploded near the finish line, the carnage, the rescues, the manhunt that shut down a U.S. metropolis, the capture of one alleged bomber and the killing of another.

Yet you can’t look away. As the authors describe the ordinary lives of five people caught up in the attack and bring them inexorably together, with the dread of knowing where and how they will become part of the same horrific afternoon, you are back in Boston again, with the sickening feeling of seeing something terrible about to happen and being powerless to stop it.

There is Heather Abbott, who lost her lower left leg in the bombing. David King, a trauma surgeon who ran the race and almost immediately began performing emergency surgery on blast victims. Krystle Campbell, who was killed by the first explosion. Police officer Shana Cottone, who was at the finish line that day and helped save two victims. And race director Dave McGillivray, who has dedicated his entire life to the 117-year-old marathon.

The account by two Boston Globe reporters, Scott Helman and Jenna Russell, succeeds in every way. It is a harrowing narrative of the events and a behind-the-scenes look at the public officials and everyday people forever changed by the attack. It is also a portrait of a major American city, its psyche and the distance runners who consider the race a sacred rite.

In Massachusetts, the authors write, “there is hardly a bigger tradition than Marathon Monday. . . . It’s a chance to breathe in a place that defines high-strung, a chance for Boston to put aside, at least for a moment, its tribalism and fractiousness, to welcome outsiders to a town not always known for its hospitality. To celebrate the top runners but also the stragglers, the strivers, and the hobbyists, all of them laced up and pointed toward the sea.”

“Long Mile Home: Boston Under Attack, the City’s Courageous Recovery, and the Epic Hunt for Justice” by Scott Helman and Jenna Russell. (Penguin)

Three spectators were killed and more than 260 injured by the two homemade bombs, pressure cookers filled with gunpowder, nails, ball bearings and other bits of metal that cut through crowds packed shoulder to shoulder at two spots near the finish line. A police officer for the Massachusetts Institute of Technology was slain days later, allegedly by 26-year-old Tamerlan Tsarnaev, described as the mastermind of the plot, and his then-19-year-old brother Dzhokhar, who was captured by police. The elder Tsarnaev died during a wild shootout with police that is one of the book’s most gripping scenes. Another is the lengthy account of a carjacking victim who escaped the brothers after they drove him around the Boston area for hours.

A year later, some victims are still struggling with their injuries, most notably the 16 people who lost one or both legs to the explosives, which were placed on the ground. (At an event that celebrates running, upper extremities were spared, except for the finger of one victim.). Almost $61 million has been distributed to the injured, and millions more are coming in July.

This year, Boston is planning an April 15 tribute to the victims, as well as the first responders and medical personnel who undoubtedly kept the death toll from rising with their skills, calm and quick decision-making. The race, with an expanded field that includes about 5,600 people who could not finish last year because of the bombing, will take place as usual on Patriots’ Day, April 21, under heightened security. Instead of the usual 500,000 spectators, organizers expect 1 million.

The authors know Bostonians — at least to the eye of someone who has never lived there — and they certainly understand marathoners. I have run many of the major-city marathons, including Boston once, and I know the magic of standing at the starting line in Hopkinton and the overwhelming emotion of finishing on Boylston Street, 26.2 miles away.

“At heart, the Boston Marathon honors something very simple,” the authors explain in the prologue. “It celebrates life’s constructive forces: good health, fellowship, hard work, discipline, philanthropy, and a belief that we can push ourselves to greater heights, especially alongside others reaching for them too. . . . To line up in Hopkinton is to put your hand up, and say, Me too.”

From there the book is a tautly written page-turner that profiles the five main characters, others and the Tsarnaev brothers, two Chechen immigrants from Kyrgyzstan whose lives fell apart as they struggled for the American dream in Cambridge. There is not much about the brothers that an attentive reader has not learned over the past year, with one important exception: The book raises the possibility that Tamerlan Tsarnaev was mentally ill, hearing a voice that commanded him at times as he turned to orthodox and then radical Islam.

Many have speculated that Dzhokhar Tsarnaev fell under his older brother’s sway, and that is the impression left here. With his parents split and back overseas, he is depicted as a dope-dealing slacker, barely hanging on at the University of Massachusetts at Dartmouth.

But there was nothing in his background to suggest that the sweet-faced former high school wrestler might be headed toward terrorism until authorities looked at his laptop after his capture and found material that promoted radical interpretations of Islam. That includes a book whose foreword was written by Anwar al-Awlaki, the U.S.-born radical cleric who helped inspire terrorist attacks against Western targets before he was killed in a U.S. drone strike in Yemen.

The book treads lightly over the decision to shut down Boston and some of its suburbs during the manhunt for the younger Tsarnaev, an unprecedented move, though it does illuminate the efforts of Gov. Deval Patrick, Boston Mayor Thomas Menino and Police Commissioner Ed Davis to cope with events that unfolded in rapid succession over five days.

Nor does it spend much time probing how a dragnet of hundreds of heavily armed law enforcement personnel could miss Tsarnaev, wounded and bleeding, hiding in a boat in a Watertown backyard. The suspect was discovered by the boat’s owner soon after the lockdown was lifted.

It is more thorough in describing the failures of U.S. and Russian anti-terrorism authorities to identify Tamerlan Tsarnaev as a threat and the missed opportunity when police did not investigate him in connection with a triple homicide in quiet Waltham more than a year before the bombing.

The authors return to their strengths as they describe a region beginning to heal. Campbell’s wake and funeral are heartbreaking; later, a memorial gazebo is dedicated by her family on her favorite island in Boston Harbor. Sean Collier, the murdered MIT police officer, is posthumously awarded a spot on the Somerville police force, which he had been preparing to join. Abbott makes the wrenching decision to have her mangled left foot amputated, agreeing to let surgeons remove healthy tissue above her ankle to improve the fit and mechanics of her prosthesis. Then she returns to running.

And McGillivray keeps a promise made to his grandfather 40 years earlier that he would run the marathon every spring until he was no longer able. Normally he did that on Marathon Monday, in the afternoon, as the race was winding down and his work was done. Last year, the bombing and its aftermath forced him to wait 11 days to set out from Hopkinton.

Though McGillivray’s post-marathon runs are part of local legend, he and his running partner tell no one of their plans. But the police, and then the media, find out as they are en route, and McGillivray, embarrassed, is greeted by sirens, a news helicopter and cheering fans as he crosses the finish line on Boylston Street, “at the very spot where evil had visited his beloved race. . . . With this run, this personal feat in defiance of the bombing, Dave McGillivray wanted to make a statement,” the authors write. “ ‘I felt, I can’t let this act of violence deter me from doing what I usually do,’ he said. Much of Greater Boston felt the same.”

Lenny Bernstein, The Washington Post’s “To Your Health” blogger, has written about the victims of the Boston Marathon bombing.