Joe Posnanski moved to State College, Pa., to write a much different book.

Posnanski imagined his biography of Penn State University’s heralded head football coach, Joe Paterno, would be about the man who, as Posnanski noted in a recent USA Today column, “always said that winning wasn’t what mattered. And yet, he won more games than anyone.” The book he was writing was based on full access to the coach and his records.

And then everything changed. Last November, Jerry Sandusky, who had coached defense alongside Paterno for 30 years, had received a great deal of credit for making Penn State into “Linebacker U” and was at one time considered Paterno’s heir apparent, was indicted by a grand jury on 40-some counts of sexual assault.

And so Posnanski found himself in the midst of a very different book, one that exists in a kind of limbo between his original goal of portraying what made Paterno tick and the natural reporter’s goal of staying abreast of a developing story.

Posnanski has written that the “book, I believe, lets the reader make up his or her own mind.”

If only the book had let me make up my mind! For this reader, Posnanski’s “Paterno” has complicated the issues of the Penn State story, re-enraged me and then left me with at least as many questions as before.

Yes, Posnanski has written a good, if frustrating, book. “Paterno” is structured, exquisitely, as a five-act tragic opera, and not just because Paterno liked opera. Paterno’s story is one of unimaginable success — a football coach who built a university — and an unimaginably precipitous fall — he lost his job, his health and his life in less than three months.

Four of the five “acts” begin with an “aria” of direct speech, taken from Paterno’s recorded or written speeches or reconstructed from his notes to set the tone for the section.

Throughout, Posnanski avoids the pitfalls of the worst sports biographies: game results. Instead of a forced march through 50 years of football, Posnanski treads lightly, mentioning only pertinent highlights from particularly big games.

A casual follower of this story might be surprised to learn from Posnanski’s book that Paterno and Sandusky were not friends; not only that, but these two men who’d worked alongside each other for 30 years “despised each other.”

Their relationship seems to have been a symbiosis of barely suppressed enmity. Posnanski mentions what the family calls Paterno’s “Why I Hate Jerry Sandusky” memo — written in 1993 — but does not quote from it. The gist seems to be that Paterno thought Sandusky had lost his fire for coaching.

If that were the case, a reader wants to know, why did Paterno wait another five years to make it clear to Sandusky that he would not be head coach?

According to the independent report headed by former FBI director Louis Freeh, that discussion took place in 1998 just a month or so before the campus police investigated Sandusky for inappropriate behavior with an 11-year-old boy in a locker room shower.

This shouldn’t be confused with a similar incident in 2001, which was reported to Paterno by graduate assistant Mike McQueary. Paterno contended to the Sandusky grand jury that he knew nothing about the 1998 assault.

Except, well, it seems he did. The Freeh report includes — and Posnanski mentions — a one-line email from May 1998. Athletic director Tim Curley is asking for an update on “Jerry,” because “Coach is anxious to know where this stands.”

In Posnanski’s words, Paterno told the grand jury he “had never heard another rumor about Sandusky, but admitted that things could have been said in his presence that he had forgotten.”

Men in their early 80s do forget things. But it strains credulity to believe that Paterno, whose players often praised his remarkable memory for things like the cheesecake their mothers had served him on recruiting visits, forgot allegations of pederasty involving an employee whom he not only hated but who had founded and run a charity for wayward adolescent boys.

This is one of many contradictions that begin to trouble the reader. Up until now, even when Paterno has been a jerk — and his players usually thought he was that — the reader has liked Posnanski’s Paterno, a Brooklyn boy who majored in English at Brown and built a rural school’s football program into a powerhouse.

Posnanski deliberately does not dwell on Sandusky and the scandal, preferring to keep his attention squarely on Paterno.

Two illustrative vignettes bookend Posnanski’s tale.

Early on, Posnanski tells the Paterno family’s “shyster” story: At a restaurant many years ago, one of the coach’s children ordered an all-you-can-eat salad. Another daughter, toward the end of the meal, snatched a slice of cucumber off her sister’s plate. The coach accused her of being a shyster, of stealing from the restaurant’s owners — it’s not an “all you and your sister can eat” place — and stormed out.

Everything mattered. That’s the story Posnanski figured he was going to tell about Paterno. “Again and again, over and over,” Posnanski writes, “Paterno told (his team): Take care of the little things, and the big things will take care of themselves.”

At the end of the book, the other little thing: Last November, Paterno and his crisis team are meeting to discuss the statement they’ll release to the public. Paterno takes issue not with the substance of the statement, but with the phrase that claims he went “to work every day for the last sixty-one years.”

“Well, I didn’t come to work every day,” Paterno says. “I was sick a couple of days and there were other things I don’t know if I’d say that’s completely honest.”

It’s a punch line, but it’s a rueful one. By this time, the little things are very much beside the point.

In that recent column, Posnanski wrote, “I believe I have written about his life with as much honesty as I have.”

I believe him, too. I wish I could say I believe Paterno.