The doubts arose almost immediately when HarperCollins announced last month that it would release a rediscovered book by Harper Lee: Did Lee – 88, publicity-shy and famously resistant to producing a follow-up to her masterpiece, To Kill a Mockingbird – really want to publish a second novel that she wrote and set aside more than a half-century ago?

Weeks later, that question remains a matter of passionate debate. Despite reassurances from her publisher, lawyer and literary agent that Lee has enthusiastically endorsed the publication, the controversy over the new book, Go Set a Watchman, has divided some residents of her home town of Monroeville, Alabama, as well as longtime friends who live elsewhere. One faction argues that Lee's mental health is too shaky for her to have knowingly authorised the new book, while the other just as vigorously affirms her competence.

Now the state of Alabama has been drawn into the debate. Responding to at least one complaint of potential elder abuse related to the publication of Watchman, investigators interviewed Lee last month at the assisted living facility where she resides. They have also interviewed employees at the facility, called the Meadows, as well as several friends and acquaintances.

It remains unclear what, if anything, will come out of the investigation, now more than a month old. One person informed of the substance of the interviews, who did not want to speak for attribution because the inquiry was ongoing, said Lee appeared capable of understanding questions and provided cogent answers to investigators.

That the state has undertaken an inquiry highlights the scrutiny that Lee’s publisher and lawyer are facing as they prepare to release one of the most hotly anticipated titles in decades. And the spectacle of a very public debate about Lee’s mental condition and true intentions has added an operatic blemish to what should have been a triumphant moment for HarperCollins and the millions of fans who have clamored for decades for Lee to produce another book.

A lot is at stake, including the legacy of one of the country's most beloved authors. Many wonder whether Watchman, which was rejected by a publisher in the mid-1950s and then rewritten as Mockingbird, will turn out to be a flawed, amateur work when it is released in July, and a disappointing coda to a career that has been defined by one outsize hit.

With an investigation involving Monroeville’s most famous resident under way, friends and acquaintances who have come forward in recent weeks have offered conflicting accounts of Lee’s mental state, with some describing her as engaging, lively and sharp, and others painting her as childlike, ornery, depressed and often confused. Several people said her condition varied depending on the day.

Lee – known to many as Nelle, her legal first name – had a stroke in 2007 and has severe hearing and vision problems. But friends who visit her regularly say she can communicate well and hold lengthy conversations if visitors yell in her ear or write questions down for her to read under a special machine. (A black marker is kept in her room for this purpose.)

Philip Sanchez, a lawyer who was a pallbearer at the funeral for Lee's older sister, Alice, last year, and visits Lee regularly, said he was not prepared to judge whether Lee was capable of consenting to publish the book. "It's a call only God or a doctor can make," he said. "I am more concerned that Nelle is content than the discussion of her cognisance."

Wayne Flynt, the Alabama historian and a friend of Lee, said the author is mentally fit and engaged and can recite long passages of literature. When he visited her a few weeks ago after hearing reports that she was depressed, they spoke about his grandson and she laughed at the stories he told. He said he believed Lee was capable of assenting to the publication of Watchman.

But he also said she occasionally had problems with her short-term memory. When he asked her about her new novel, he said, she seemed to be "in her own world" at first and asked, "What novel?" Reminding her of Watchman, he told her "You must be so proud," and she responded with "I'm not so sure anymore," Flynt recalled.

The only statements from Lee about the new publication – affirming her enthusiasm – have come through her lawyer, Tonja B Carter, who handles her day-to-day affairs. Carter came across the manuscript in August and negotiated the book deal with HarperCollins. Over the course of a week, Carter did not return a phone call and text messages seeking comment, and she did not make Lee available for an interview. A lawyer for Carter, Bobby Segall, declined to comment. In a previous interview with the New York Times, she described Lee's excitement that Go Set a Watchman would be published and stressed she would never go against the author's wishes.

One person who said he had filed an anonymous complaint with the state is a doctor who has known Lee for years. The doctor said in an interview that he had called Alabama's adult protective services hotline and asked the state to investigate whether Lee was too infirm to have fully consented to the publication of Watchman.

The doctor, who has not treated Lee and asked to remain anonymous because of the divisive nature of the issue, said he had been alarmed by reports of her frailty and by an account from someone he trusted who had visited Lee last autumn after the death of her sister and said she was largely uncommunicative, lying in a foetal position in bed in the middle of the afternoon.

The investigation is being led by the state’s Human Resources Department with the help of the Alabama Securities Commission, which, among other things, works to prevent financial fraud against the elderly. Barry Spear, a spokesman for the department, said he could not comment on any investigation, noting that such inquiries were confidential. But he said that investigations into elder abuse were done at the discretion of the department, based on an initial assessment of the complaint, and that they could involve law enforcement if there was evidence of financial exploitation.

Case workers generally talk to people who may be victims to evaluate their physical, mental and emotional state, and they interview doctors, family members, caretakers and friends, Spear said. In some cases, an investigation may involve subpoenaing financial and other records. Among the records that may be available are cognitive assessments of Lee by the staff of the Meadows. The facility agreed to make such monthly assessments on each resident as part of a settlement of a 2014 review by inspectors of the Alabama Department of Public Health.

Several of Lee's friends and two of her caretakers said they had been interviewed by investigators. Marcella Harrington, an aide paid by Lee's lawyer to sit with her regularly, said in an interview that investigators had asked her if Lee could recognise friends and if she was receiving proper care. Harrington said she told them that Lee was lucid and aware of the book. Asked by a reporter whether Lee was mentally alert, Harrington said, "As far as I know, she is."

Others who met investigators painted a different picture of Lee's condition. Writer Marja Mills, who lived next to the Lee sisters in Monroeville for about 18 months beginning in the autumn of 2004 and wrote a book about the experience, The Mockingbird Next Door: Life With Harper Lee, recently met investigators. She shared excerpts from a transcript of what she said was a recorded conversation she had in 2010 with Alice, who died in November at 103. In the conversation, recorded with Alice's consent, Alice described her sister as having serious memory lapses during discussions about her personal affairs, Mills said.

“She doesn’t know from one minute to the other what she’s told anybody,” Alice said of her sister, according to those excerpts. “She’s surprised at anything that she hears because she doesn’t remember anything that’s ever been said about it.”

Lee's publisher and literary agent have dismissed suggestions that she is too mentally infirm to consent to publishing Watchman. Michael Morrison, the president and publisher of HarperCollins, said he and Jonathan Burnham, the senior vice president and publisher of Harper, visited Lee over two days in February, the week after the new book was announced. "She was in great spirits, and we talked about how much we love Go Set a Watchman and the details of the publication," Morrison said in a statement to the New York Times. "It was a great meeting, and as expected, she was humorous, intelligent and gracious."

Through a HarperCollins spokeswoman, Morrison said the company was aware of the state's inquiry but had not been contacted by investigators. Andrew Nurnberg, the agent handling international rights for Watchman, has brushed off reports that Lee is somehow being taken advantage of as "nonsense." But sceptics point to a different picture of Lee that emerged in a 2013 lawsuit she filed against her former literary agent, in which she said he had "engaged in a scheme to dupe" her by hiding royalty payments and appropriating the copyright to Mockingbird. In the lawsuit, which was confidentially settled, she was portrayed by one of her lawyers as infirm and vulnerable to those she trusts.

As the debate over Lee’s condition continues, amplified by the investigation, what was once a source of pride in this small town is now a flash point, with much of the animosity settling on Carter, her lawyer. Some residents of Monroeville, a town of about 6,300, seem resentful of her, calling her aggressive and needlessly protective of her client in ways that have isolated Lee from some longtime friends.

Others say Carter is a dutiful steward of Lee’s affairs and have noted that Alice Lee retained Carter as the lawyer on her will. “Ms Carter has been with the Lee sisters for many, many years, and she is a first-rate lawyer,” said Greg Norris, a probate judge and president of the Monroe County Commission. Norris worries that the fractious debate over the new book could erode Monroeville’s literary legacy. “I just don’t know why people would be so negative,” he said. “We are a poor rural county, and this new book puts us on the map again.”

New York Times