“The Quran gained a popular readership among Protestants both in England and in North America largely out of curiosity,” says Denise A. Spellberg, a history professor at the University of Texas at Austin and author of Thomas Jefferson’s Qu'ran: Islam and the Founders. “But also because people thought of the book as a book of law and a way to understand Muslims with whom they were interacting already pretty consistently, in the Ottoman Empire and in North Africa.” When Jefferson bought his Quran as a law student in 1765, it was probably because of his interest in understanding Ottoman law....