He took over James McEuen's London shop in 1728, having once been his apprentice. Early in his career, he sold books for the Society for the Encouragement of Learning, nurtured James Thomson as his principal author, and acted as London agent for the Foulis brothers and Alexander Kincaid. Millar's business success rested chiefly on the shrewd purchasing of copyrights in both established and new works, his generosity to authors—leading S. Johnson to comment that Millar had ‘raised the price of literature’—and (unlike Dodsley) his cultivation of the novel as a publishing enterprise. Among his celebrated authors were Fielding, Hume, Gibbon, and Young. He also invested in reference works that proved lucrative, including Johnson’s Dictionary and Chambers’s Cyclopaedia.
From The Oxford Companion to the Book in Oxford Reference.