The book’s title suggests, tantalizingly, a close bond during those school years in the mid-1970s. A more accurate title might have been “Four High School Acquaintances of the Author.” Cohan was “friendly with” each one, he writes vaguely, “to varying degrees.” One was two years ahead, one a year behind. He was closest to Kennedy. But after high school, he fell out of touch with them all.

Piecing together their stories, he confesses, was “a reporting challenge.” He relied heavily on friends and family members. Some declined to talk. The profiles are touching. They are also impressionistic and inconclusive. Because the book has neither endnotes nor a bibliography, it is not always easy to weigh the credibility of conflicting assertions.

Cohan makes liberal use, too, of published accounts from disparate sources — from The New York Times and The Associated Press to People magazine, Vanity Fair, The National Enquirer and the ever-expanding library of tell-all books by the likes of a Kennedy girlfriend, former Kennedy colleagues, a Kennedy nanny.

A reader might wonder how this book was conceived and evolved. It’s maybe an obvious question, but why does Kennedy, whose story is well known, end up with twice the pages given to anyone else? Why is the opening chapter devoted to two more Andover graduates — one of whom died from cirrhosis in his late 30s, having never recovered from a head injury suffered in a car accident caused by an Andover friend driving too fast and too drunk at the end of their second year at Cornell?

I couldn’t help thinking about what story Cohan actually intended to tell. Two of his previous books, on the Duke lacrosse scandal and the investment bank Lazard Freres, examined powerful institutions, like Andover, of which he had once been a part. This time, his conclusions, such as they are, appear to have less to do with the prep school world than with what he refers to as “the fragility of life.”

“Andover is a place where very big dreams are formed, nurtured and encouraged without the slightest bit of irony,” Cohan writes. When they “get snuffed out,” the damage can be substantial — “if only because it reveals the stark truth that no one is exempt from the one unavoidable aspect of life: death.”

Who knew?