And although the overall growth in electronic book sales in the U.S. has shown signs of flattening in recent months, downloads in languages other than English are soaring.

According to Amazon, sales of foreign-language e-books in English-speaking markets (including the U.S.) were expected to rise 40% in 2013 compared with 2012, once final sales are tallied. Meanwhile,, an Amazon subsidiary, said that foreign- language audio book sales are increasing at a more than 25% annual rate.

"Digital removes all the obstacles you have with a printed book," said Carmen Ospina, director of digital development at Random House Mondadori, which is based in Barcelona. The U.S. makes up 19% of the publisher's worldwide e-book sales, compared with less than 10% a year ago, she said.

This month, Ospina said, the publisher will release Chilean author Isabel Allende's new novel, "El Juego de Ripper," simultaneously in the U.S., Spain and Latin America. In the U.S., a Kindle or Apple iBook edition will cost $9.99, about half the price of a hardcover copy.

The digital expansion in Spanish has also had spillover benefits for printed books in Spanish as foreign publishers grow more optimistic about the U.S. market.

Last year, the Library of Congress acquired 9,974 titles published in Spain, compared with 8,178 in 2009, according to Beacher Wiggins, the library's director of acquisitions and bibliographic access. Independent Publishers Group, a national distributor based in Chicago, has seen its revenue from Spanish-language print books jump 40% over the last five years, according to Diana Calice, head of Spanish books at the company.

And in July, the paperback version of "Inquebrantable," the autobiography of deceased recording artist Jenni Rivera, hit the No. 1 spot on all of, outselling every other book on the e-commerce site — including "Unbreakable," the English version of the same memoir.

It wasn't always thus. For decades, foreign publishers largely ignored America's Spanish-speaking population.

That changed after the landmark 2000 U.S. census revealed that 12.5% of the U.S. population, or more than 35 million people, were of Hispanic origin, an increase of more than 57% from a decade earlier.

Overseas publishers quickly opened offices in the U.S., while one of Spain's three largest publishers, Grupo Planeta, opened a warehouse in Miami. Online booksellers created Spanish Web pages. And American publishers launched domestic imprints in Spanish.

"Publishers suddenly realized there are a lot of Latinos in the U.S. and they could be worth a lot of money," said Arancibia, who no longer works at Barnes & Noble and is a consultant to the industry.

But not everyone hit pay dirt. Without Spanish-speaking book buyers on staff, some booksellers chose titles that flopped with U.S. Latinos. Most Mexican immigrants, for example, have little interest in Nicaraguan politics or travel to Spain's Canary Islands.

Hastily translated English-language bestsellers, meanwhile, were often riddled with spelling and grammatical errors. Sales were tepid and publishers withdrew; HarperCollins, for example, dramatically scaled back its Spanish-language imprint Rayo, which launched in 2000 and had been publishing 75 titles a year.

"They thought they could come in and immediately grab 15% or 20% of the U.S. market," said Alex Correa, president and chief executive of Lyndhurst, N.J.-based Lectorum Publications, one of the country's oldest Spanish-language publishers and distributors. "In fact, they were fighting over perhaps 3% of the total."

Still, the publishing industry had awakened to the market's potential.

By 2010, the U.S. Hispanic population had climbed past 50 million. That year, Barnes & Noble launched its Spanish-language Nook site. Other sites followed. Today, even foreign retailers are attempting to get a piece of the market. In April,, based in Argentina, entered the U.S. with a catalog of 50,000 e-books in Spanish.

Getting out the word about the flood of new books remains a challenge, however.

Spanish-language media in the U.S. pay scant attention to books and rarely host authors on talk shows. Leading industry publications, including Kirkus Reviews and Publishers Weekly, which are highly influential among buyers at retailers and libraries, do not review foreign-language titles.

Still, Publishers Weekly published two special Spanish-language supplements last year and is considering a monthly column on Spanish-language books, according to Editorial Director Jim Milliot.

Meanwhile, LeaLa, a Spanish-language book fair launched in Los Angeles in 2010, is expanding quickly. Nearly 85,000 people attended this year's event at the Los Angeles Convention Center in May, up from 36,000 in its first edition.

The market shift is also benefiting authors.

A year after publishing her first novel in 2006, "Across a Hundred Mountains," Whittier author Reyna Grande published it in Spanish. In 2012, she released a new memoir in English and added a Spanish translation when the paperback came out in April. And she's now at work on a historical novel about the Mexican American War that will come out in Spanish and English.

"I've noticed that having it in Spanish helps increase sales in English and vice versa," said Grande, who does her own translations. "I plan to do all my work in both languages now."