Which sacred text has consistently been the highest-selling book product in history, with publishers reporting approximately how many copies sold worldwide?

Throughout history, religious and philosophical texts have not just been spiritual guides but also significant commercial products. The publishing and distribution of these texts represent a massive industry with fascinating business trends and consumer behaviors. This trivia question explores an interesting aspect of this market that reflects both spiritual significance and consumer psychology in the modern era.

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The Bible, with estimated sales of over 5 billion copies
The Quran, with estimated sales of over 3 billion copies
The Bhagavad Gita, with estimated sales of over 2 billion copies
The Book of Mormon, with estimated sales of over 1 billion copies