Wizard Harry Potter has cast his spell over readers in 43 countries, magically transforming the life of the penniless, single mom who turned his adventures into the Pokémon of world literature.

Author Joanne Kathleen Rowling has earned $30 million from the first three Harry Potter books, making her the third-richest woman in Britain, and is poised to see her personal fortune jump to $80 million in the coming months as the latest tome leaps off bookstore shelves like enchanted broomsticks.

But J.K. Rowling’s success also has its darker side. Her husband, a former drug addict, has emerged from her shadowy past to open the door of Rowling’s personal chamber of secrets.

He is demanding access to their daughter, Jessica, who will be 7 this month. He has refused to sign a divorce agreement and, although he claims he has no interest in her money, British experts familiar with the case say he might be entitled to as much as half of Rowling’s fortune.

“I am not interested in Rowling’s money,” insists Portuguese journalist Jorge Arantes, 32, who shared J.K. Rowling’s life for three years. “I only want to see Jessica again.”

Arantes claims he helped Rowling frame the Harry Potter stories, which have had such a remarkable impact on children – and adults – the world over. And he has tried to shatter some of the myths that have grown up around the creation of the Harry Potter phenomenon.

Arantes first emerged from the shadows several months ago, when he told London’s Daily Express newspaper the story of his whirlwind romance and doomed marriage to the then-unknown Joanne Rowling.

It was a sexually passionate relationship that ended in violence and bitterness. She was a 25- year-old teacher who had come to Porto, Portugal. He was a 23-year-old student with his eye set on a career in journalism. He spotted her drinking with some friends in a cafe, was drawn to her piercing, aquamarine eyes, and tried to pick her up.

“Immediately, there was a connection between us,” he says. “Joanne could not speak any Portuguese, but my English was good. We both realized we had a great deal in common with our love of books.

“I remember her saying she was rereading Jane Austen’s ‘Sense and Sensibility,’ which I had also read.”

Arantes said she told him about an affair she had with another Portuguese man, and about a love affair with a man in England. When the night ended, they exchanged telephone numbers – and a kiss.

Two days later, he says, they had their first date – and ended up in bed.

“Before we knew what was happening, she was back at my flat and we spent the night together,” he says.

“There was nothing sordid about it. We were simply two young, independent people enjoying life.

“After that night, Joanne and I saw each other two or three times a week. It was an intense and passionate relationship.”

It was also tempestuous. Their frenetic lovemaking was punctuated with furious arguments.

“We were always either in heaven or in hell,” he says.

Soon, they were living together in a shabby two-bedroom apartment with a tiny kitchen. Among the belongings she brought to their home, according to Arantes, was a well-thumbed copy of J.R.R. Tolkien’s classic “Lord of the Rings.”

Several months later, Joanne discovered she was pregnant. It was unplanned, and both were afraid of the responsibilities parenthood might bring. But just as they had begun to look forward to the birth of the child, tragedy struck. Joanne miscarried.

When she conceived again a few months later, Jorge asked her to marry him.

One of the publicity myths surrounding Harry Potter is that J.K. Rowling, by then a penniless, single mother in Scotland, wrote the first book in an Edinburgh cafe while baby Jessica slept at her side.

According to that version, Rowling was too poor to afford child care so she could work, but didn’t qualify for a place in a free, state-run nursery.

Each day, as the story goes, Rowling would take the baby to a park, then rush to write her masterpiece in Nicholson’s Cafe in Edinburgh as soon as Jessica was asleep. The original idea for the book is said to have come to her while her mind wandered during a long journey on one of England’s gloomy trains.

But Arantes says Rowling had begun writing the Harry Potter books long before, when she was pregnant for the first time. She kept her writing secret for a time, then showed her work in progress to her husband.

“I am proud to say that I was the first person to read about Harry Potter,” Arantes says.

“It was obvious to me straight away that this was the work of a genius. I can still remember telling Joanne, ‘Whoa! I am in love with a great, great writer.’ Even in those days, Joanne had a great talent for structure. I never doubted that it would be a success.”

He says they discussed the stories, which Rowling found helpful. “We studied each other’s work and made suggestions,” says Arantes. “When I told Joanne to change something, she would usually make an alteration.”

He claims she had planned the full series of seven books – because she believed the number seven has magical associations.

But the magic was already evaporating from their marriage when Jessica was born July 27, 1993. Two months later, Arantes admits, he ordered his wife out of their apartment.

“She refused to go without Jessica, and, despite my saying she could come back for her in the morning, there was a violent struggle,” he says. “I had to drag her out of the house at 5 in the morning, and I admit I slapped her very hard in the street.”

Joanne made her way home to Edinburgh with her baby daughter. Three months later, Arantes followed her and says he tried to reconcile. But Joanne told him their marriage was over.

Even so, Arantes told The Express last fall, he found a way to make his trip worthwhile.

“Fortunately,” he said, “I found another girl for the rest of my holiday, but it upset me that when I was leaving, she would not let me see Jessica.”

Despite the emotional wreckage, Rowling continued to work on her book. She had so little money, she says, that she had to retype her manuscript rather than spend the money to have it copied.

When she finally found a publisher, Bloomsbury Press, she received an advance of about $4,000 for the first Potter book, “The Sorcerer’s Stone” – a pitifully small amount, even by the standards of British publishing houses.

The U.S. publisher Scholastic bought the rights to the book about a year later, and since then, Rowling and Harry have broken publishing records.

Meanwhile, Arantes’ life was falling apart. He lost his job as a television journalist and descended into a nightmare of drug addiction. His 70-year-old mother, Marilia Rodrigues, told the London Daily Mirror recently that he stole family heirlooms and jewelry to feed his drug habit.

“He still loved her very much and was heartbroken when they parted,” Rodrigues said of the marriage. “He still believes they could get together again, and he would take her back at the drop of a hat. He just wants her and his daughter.”

Arantes says he has recovered from his drug addiction and is living in a small apartment in the Paris suburb of Clichy with his brother, Justino, a travel agent.

Rowling, who shares a mansion worth close to $1 million with her daughter, rarely talks about her marriage, but recently told the Times of London: “I married on Oct. 16, 1992. I left on Nov. 17, 1993. So that was the duration of what I considered to be the marriage.

“Obviously, you do not leave a marriage after that very short period of time unless there are serious problems. I’m not the kind of person who bales out without there being serious problems.

“My relationship before that lasted seven years. I’m a long-term girl. And I had a baby with this man. But it didn’t work. And it was clear to me that it was time to go, and so I went.

“I never regretted it.”

Despite Arantes’ protests that he is not interested in Rowling’s money, British divorce attorneys familiar with Portuguese law say that if there is no prenuptial agreement, either partner’s wealth must be shared in what is known as “a community of assets.”

Arantes’ share in that community would make him immensely wealthy, and in a powerful position to pursue his legal claims to visitation with his daughter.

British law, however, might permit Rowling to divorce Arantes unilaterally, as they have not cohabited for several years. But if she takes that course, experts say, she might still be forced to acknowledge his rights as the child’s father.

And that, sources say, she’s determined she will never do.