Which retail innovation first allowed for mass distribution of affordable religious texts to the general public in the 15th century?

The publishing and distribution of religious texts has evolved dramatically over centuries, from hand-copied manuscripts to modern retail innovations. Religious book retail has become a sophisticated industry with specialized marketing, packaging, and sales strategies. This trivia question explores a significant modern retail innovation that revolutionized how sacred texts reach believers worldwide.

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Gutenberg's printing press with movable type
Monastery-based subscription services
Royal court publishing patronage systems
Merchant guild distribution networks