“This book aims to capture a life but is not a conventional biography, because – despite her novel’s huge impact – [Harper] Lee’s writing life has been brief, and her personal life has been intensely private,” Charles Shields writes in “Mockingbird: A Portrait of Harper Lee” (Henry Holt, 338 pages, $25). In other words, this is an unauthorized biography that Ms. Lee would have no truck with. On several occasions, Mr.Shields tried to enlist the novelist’s assistance for “Mockingbird” but Ms. Lee’s lawyer (her formidable older sister, Alice) rebuffed him.

Why do biographers persist in the face of such obstacles? Mr. Shields provides the standard answer: “Despite her desire for privacy, I believe it is important to record Lee’s story while there are still a few people alive who were part of it and can remember.” In her 80s, Ms. Lee remains very much alive, if wary of anyone wishing to know about the author and not just about her book.

I sympathize with Mr. Shields, having produced my own unauthorized biographies of living figures. Indeed, Mr. Shields might have made more of his rationale. “To Kill a Mockingbird” has not merely been a best seller, a landmark book in the history of the South and of race relations – and a perennial novel to teach in more than three quarters of the country’s classrooms – it has changed lives. Readers go in search of Ms. Lee as they go on pilgrimages to shrines. Surely they have a right to know about their destination.

Like other unauthorized biographers, Mr. Shields emphasizes that he is a man under ethical restraints: “I have tried to balance her desire for privacy with the desire of millions of readers who have long hoped for a respectful, informative view of this rarely seen writer.” Like J.D. Salinger, Ms. Lee disappeared from view even as her work became a national treasure. Early on she did give interviews, but then she retired from public scrutiny as prospects for a second novel faded from view.

Respectful? That means Mr. Shields will not speculate on his subject’s life, even though she never married, never seems to have had a beau, and wore mannish clothes. “I cannot say if she is homosexual,” Mr. Shields admits. He rules out any surmises and overlooks certain topics because he does not want to psychologize or “risk producing errors that might find their way into future accounts of Lee.”

Honestly, Mr.Shields, what are future biographers going to do except correct your errors (all biographers make errors) and dig deeper into Ms. Lee’s life? Although he claims to have dealt with something like 600 friends, associates, and acquaintances of Ms. Lee’s (about 75 of them are cited in his notes), I have to wonder how hard he pressed them. Dealing with Southern ladies is difficult because the biographer has to appear to be a gentleman, but truth to tell, writing lives is not a gentlemanly occupation, and I would have preferred some rude speculation over the bland reporting that too often results from Mr. Shields’s desire to be above reproach.

I do admire his diligence. He consulted alumni directories of schools Ms.Lee attended and joined a reunion service to track down her classmates, but why he should think his methods “unorthodox” is beyond me. These sorts of maneuvers are what many unauthorized biographers do after traditional methods such as looking for letters in archives have been exhausted.

The chief value of “Mockingbird” – and it is an extraordinarily important one – is Mr. Shields’s meticulous and fascinating account of how Ms. Lee came to write her novel, which tells the story of how Atticus Finch, a small-town lawyer, came to defend an African American man unjustly accused of raping a white woman. Ms. Lee benefited from excellent timing – her novel appeared in 1960 during the Civil Rights movement – but even more significantly, she wrote about her characters with deep affection and knowledge that continues to touch readers from later generations.

Yet the novel might very well not have seen the light of day if Ms. Lee’s New York friends, Michael and Joy Brown, had not bankrolled her, providing funds that allowed her to quit her full-time job for a year and produce a draft of her novel. Ms. Lee had been in New York City for almost a decade, eeking out a handful of unpublished short stories, after having dropped out of law school at the University of Alabama.The gift of money not only gave her time; it was, as she recognized, an act of love, a testament of faith in an untested writer.

And here lies the chief value of biography. It is often said that there are no “mute inglorious Miltons.” The phrase comes from Thomas Gray’s “Elegy Written in a Country Churchyard” (1750), a poem that every biographer should cherish because it gives the lie to the idea that anyone who really wants to write will do so, no matter how dire the obstacles. Gray insisted:

Full many a flower is born to blush unseen,
And waste its sweetness on the desert air.
…
Some mute inglorious Milton here may rest,
Some Cromwell guiltless of his country’s blood.

Biographers know that this is so: Talent plus circumstances make or break the writer. In Ms. Lee’s case, the intervention of friends and the work of an astute editor, Tay Hohoff, made the birth of “To Kill a Mockingbird” possible.

Ms. Lee never again found precisely this constellation of support. She tried a second novel, then a nonfiction novel, but nothing quite worked; none of it met the standard set by her first novel, and so she lapsed into silence. Much the same, by the way, happened to her friend, Truman Capote, who relied on Ms. Lee during the months he researched “In Cold Blood” in Kansas. The fey Capote never could have retrieved the story of the Clutter murders without the shrewd and stalwart Ms. Lee, who accompanied him to Kansas and assisted him in research and interviewing, although Capote never admitted as much. And he never again was able to come near the achievement of his stupendous true crime novel.

Biography, more than any other genre, reveals the concatenation of events and personalities. “Mockingbird,” whatever its shortcomings, demonstrates that truth quite brilliantly and is thus worth our respect and study.

crollyson@nysun.com