Linschoten's Itinerario
Jan Huygen van Linschoten left the Netherlands as a young man, went to Spain and Portugal and in 1583 sailed to Goa in the service of the Portuguese archbishop. He stayed until 1588. During those years he collected what he could of the Portuguese route information, which the Portuguese crown treated as a state secret.
Back in the Netherlands he took part in the Dutch attempts of 1594 and 1595 to find a northeast passage to Asia, and then published what he had gathered: the Reysgeschrift, a set of sailing directions, in 1595, and the Itinerario, a description of the East with engravings and charts, in 1596.
The effect
The books were read closely. The first Dutch expedition to the East Indies sailed in 1595 under Cornelis de Houtman, and the Dutch East India Company was founded a few years later. The Itinerario was translated into English in 1598 and into several other languages.
It was a rare case of a book that changed trade routes: a few hundred pages of copied directions that removed a large part of the Portuguese advantage.