Who was Huguette?

To some who knew the late copper heiress Huguette Clark, she was an oddball recluse who wasted her last decades in a hospital room, while her spread at 907 Fifth Avenue — a trio of co-ops spanning 42 rooms — sat as an empty, haunted museum of antique dolls. Distant family members, meanwhile, saw her as an incapacitated dupe at the mercy of bloodsucking money managers and caregivers.

Those caregivers, however, considered her the quick-witted benefactress who willingly cut them checks for tens of thousands of dollars.

Not surprisingly, her 2011 death at age 104 sparked a court battle over her $308 million estate.

But who was Huguette, really? That’s the question Pulitzer Prize–winning journalist Bill Dedman and Paul Clark Newell, Jr., one of Huguette’s cousins, seek to answer in “Empty Mansions: The Mysterious Life of Huguette Clark and the Spending of a Great American Fortune,” which will be published this month.

An ambitious and clearly written account of Huguette’s life, “Empty Mansions” offers meticulous details on her finances, appraisals of her personality from her closest confidantes, laughably specific descriptions of her opulent homes and even — courtesy of phone calls she exchanged with Clark Newell — scraps of conversation in her own voice.

And yet, “Empty Mansions” fails to solve the puzzle of Huguette Clark. Disappointingly, the motivations of the cloistered scion remain as elusive as ever.

To Dedman and Clark Newell’s credit, they avoid the trap of other historical writers who reconstruct the thoughts of their long-dead subjects. When they have people to interview — a bevy of living Clark descendants or Huguette’s nurse, Hadassah Peri, who received almost $32 million from her elderly charge — the pages jump with life. Unfortunately, the first half of the book, which focuses on the early years of Huguette’s father, W.A. Clark — a frontiersman who made his fortune in banking and copper — is dry.

Indeed, “Empty Mansions” is at its best when investigating the nooks and crannies of Huguette’s personality, and weighing whether she was a victim or not. (The authors seem to come down in favor of her aides, noting that almost none of her extended family members visited her.)

In many ways, “Empty Mansions” portrays Clark as a normal person, despite frequent speculation that she must have been mentally ill. For one, she was extremely generous — possessed of “a fairy tale checkbook, one that was refilled whenever it ran out of magic beans,” the authors note. “The woman was an eccentric of the first order,” her doctor, Henry Singman, told the authors. “[But] I didn’t think her behavior was that of one suffering from a psychiatric illness.”

Born in Paris in 1906, Huguette was the youngest daughter of W.A. and his second wife, Anna LaChapelle, a decades-younger woman whom he married in a secret (and possibly fabricated) ceremony that only came to light years later. W.A. disappeared from the history books, but Dedman and Clark Newell do an admirable job of exhuming his life story. A man whose fortune rivaled those of Vanderbilt and Carnegie, Clark got turfed from his U.S. Senate seat on bribery charges, and then won the office back after Montana’s lieutenant governor appointed him as his own replacement. He also purchased and subdivided the land that became Las Vegas.

As a youngster, Huguette crawled the halls of 962 Fifth Avenue, a $10 million mansion her father spent 14 years building, but which was later destroyed to make way for apartments. As those who have followed her story know, she was married only briefly, to the son of her father’s accountant, and never seemed to recover from the sudden death of her sister in 1918.

Shortly after W.A. died in 1925, Huguette and her mother moved into a 5,000-square-foot apartment at 907 Fifth Avenue that cost $12,000 a year to rent, or $150,000 in today’s dollars. Anna paid a piddling $63,000 (or $540,000 today) to purchase the unit when the building went co-op in the 1950s.

Eventually, Huguette would also own two units on the eighth floor, as well as the family’s 10,000-square-foot California estate, Bellosguardo (she preserved it, down to the 1933 Cadillac limousine parked in the garage) and a 14,000-square-foot Connecticut mansion called Le Beau Chateau, where she never set foot. (Hedge fund manager Boaz Weinstein ultimately paid $25.5 million for the 12th floor of 907 Fifth Avenue, while most of the eighth-floor units sold to private equity manager Frederik Iseman. Part of the eighth floor is currently on the market for $6.5 million.)

There’s no question that Huguette was unusual. After Anna died in the 1960s, the younger Clark withdrew from society. In the early 1990s, when she was already living in a hospital room, she recreated her mother’s bedroom in her own apartment, spending $7 million in today’s currency to replicate the heavy oak furniture and Louis XV mantelpiece. She could have had the furniture moved, the authors explain, “but then, well, the furniture would no longer be in [Anna’s apartment].”

“During that time,” they continue, “Huguette never walked into either bedroom, never spent a night there again, seeing the results of the renovation only in photographs brought to her hospital room.”

And why did she close those hospital blinds on her palatial co-ops and country estates? The answer, frustratingly, is yet another one Clark has taken to her grave.