As seen in The Economist:
The market for books in Spanish is thought to be the second-largest in the world. It is the biggest for books in translation, which account for about a fifth of the 120,000 Spanish titles published each year. With sales up by 7.5% in 2005—growth is strongest in Argentina, Mexico and Colombia—it is expanding faster than many other book markets. Since many of the world’s 400m Spanish-speakers live in developing countries, it has great potential: literacy rates are high and incomes are rising. (Ibero-American publishing, which also includes books in Portuguese, is worth about $6 billion a year.)…
In some respects, the Spanish-language market is coming to resemble publishing in English. There has not been a strong tradition of blockbusters in Spanish, says Antonia Kerrigan, a literary agent based in Barcelona, but last year La Catedral del Mar, 
a first novel, sold 1.5m copies, making it Europe’s leading seller and one of the top five in the world. There is also new interest in foreign translations of books written in Spanish. Gabriel García Márquez’s “Love in the Time of Cholera” was recently a bestseller in America thanks to a Hollywood film, and he was treated like a rock star at FIL. He is not alone: in 2006 Javier Sierra’s “The Secret Supper” also sold well in English.