“Pinochet was tormented by an intense inferiority complex, which he tried to deal with by collecting books,” said Cristóbal Peña, an investigative journalist whose 2013 book, “The Secret Literary Life of Augusto Pinochet,” explores the evolution of the dictator’s library, which included roughly 50,000 books and has been valued conservatively by rare-book experts at about $3 million.

General Pinochet, the son of a customs inspector and an average student in military school, was often overshadowed by brilliant peers like Gen. Carlos Prats, an interior minister and commander in chief of the army during Salvador Allende’s government.

But while General Pinochet was rarely admired for his intellect, he grew to be feared for his Machiavellian instincts. After replacing General Prats as head of Chile’s army in 1973, he led the coup that toppled Mr. Allende, then went about eliminating rivals like General Prats, who was killed together with his wife in a 1974 car bombing in Buenos Aires orchestrated by Chile’s intelligence agency.

While overseeing such operations, General Pinochet steadily collected books, often quietly ordering volumes through a small network of booksellers in the old center of Santiago or requesting diplomatic personnel posted in Chilean missions abroad to find certain works. All the while, he paid for the books with discretionary funds under his control.

The Pinochet library might never have come to light if not for investigations into the dictator’s secret bank accounts at various financial institutions, including some in the United States, which investigators believe to have held more than $20 million. He faced charges of embezzlement and tax evasion, in addition to legal battles over rights abuses, before his death in 2006, at 91.