My edition of the book has an introduction by PD James in which she states:
"Collins was meticulous in his research; it was a matter of pride in him to get the historical, forensic, and medical details right. He seems to have read several standard books on India, where the opening section of the novel is set, and corresponded with a member of the Indian Civil Service. He obtained information about the Koh-i-Noor diamond from a book on precious stones published in 1865, and he claims that he verified 'the physiological experiment which occupied a prominent place in the closing scenes of The Moonstone... not only from books but from living authorities as well.' He himself was one of those authorities. He took large doses of laudanum to assuage the agonies of gout, and the portrait of Ezra Jennings, the opium user, is partly autobiographical."
It's interesting to me that Collins tried to make his book as realistic as possible. He's known as a "sensationalist" writer. Anthony Trollope, who was a friend of Collins, wrote in 1883 that "All this [Collins being sensational] is, I think, a mistake, which arises from the inability of the imperfect artist to be at the same time realistic and sensational. A good novel should be both, and both in the highest degree.... Let an author so tell his tale as to touch his reader's heart and draw his tears, and he has, so far, sone his work well. Truth let there be -- truth of description, truth of character, human truth as to men and women. If there be such truth, I do not know that a novel can be too sensational."
These thoughts provide for me a helpful foundation for reading the book.