Here's why:
* No universal sales tracking: There's no central authority that tracks book sales across all Spanish-speaking countries and throughout history.
* Varying definitions: What constitutes a "Spanish" book is also subjective. Do we include books written in Spanish by authors from other countries? Do we count translations?
* Historical data limitations: Records of book sales from the past are often incomplete or nonexistent.
However, there are some books that are widely considered to be bestsellers in the Spanish-speaking world, including:
* Don Quixote by Miguel de Cervantes: This iconic novel is often cited as the most important work of Spanish literature and has been translated into numerous languages.
* One Hundred Years of Solitude by Gabriel García Márquez: This masterpiece of magical realism is considered one of the most important Latin American novels of the 20th century.
* The Shadow of the Wind by Carlos Ruiz Zafón: This suspenseful novel has been a global bestseller and translated into over 40 languages.
* The Alchemist by Paulo Coelho: This philosophical novel has sold millions of copies worldwide and is particularly popular in Spanish-speaking countries.
Ultimately, the most sold Spanish book is a matter of speculation and debate. These are just a few examples of works that have achieved significant popularity and cultural influence in the Spanish-speaking world.