“For her it’s money and continuity that she couldn’t find any other way,” Elena Ramirez, the director of the Spanish publisher Seix Barral, said. “For him it’s a way to finally put his feet in a land where he tried three times before.” She continued, “I think it’s a very clever move for both.”

Over the years, Ms. Balcells changed the rules of Spanish publishing. Before, writers would sign open-ended contracts with publishers, who gave meager advances and took near-total control of all rights. Ms. Balcells began negotiating better advances and fixed-term contracts, as well as complex licensing and rights arrangements. Today, she is fighting to get her writers better deals for electronic and film rights.

Ms. Balcells’s parties are legendary. Once, she hosted a dinner for the Mexican novelist Carlos Fuentes and his wife. When their plane was delayed for hours, she had the dinner served, then had the entire table cleared and set again so that when the couple finally arrived it appeared as if the party was just starting.

“She’s a force of nature,” Ms. Allende, the Chilean novelist, said in a telephone interview. “She’s generous and splendid and over the top.” Ms. Allende said that after Ms. Balcells sold translation rights for her first novel in 1981, she invited the writer to a party at her home in Barcelona. “I looked like a peasant, I was coming from Venezuela, I had no idea what the literary world was all about, I’d never read a book review, never studied literature,” Ms. Allende recalled. “And she received me as if I had been a famous writer already.”

For a woman who went on to befriend members of the Spanish royal family and most prime ministers (after the Franco era, which ended in 1975), Ms. Balcells came from humble origins. She grew up in a small village in Catalonia in a home without heat or running water. She studied business, but has no university degree.

“I never wanted to be important,” she said. Under Franco, when a woman couldn’t open a bank account without the signature of her father or husband, “I wanted to be independent, autonomous at a time when a woman without a rigorous education, without a powerful family, couldn’t choose what to do on her own,” she added.