Holograph letter to an unknown correspondent

This letter is a kindly response to an admirer of his historical novel The White Company. Conan Doyle proposes to send him a photograph and also pens a “little bibliography” with these famously dismissive comments:

Then there is a little group of detective books, which arose from my irritation at the fact that the detective of fiction appears always to attain his results in a perfectly arbitrary fashion without any process of reasoning or thought. I only meant to write one little book, “A Study in Scarlet” to show what I thought to be the true deductive & analytical solver of problems, but the success of it made me do “The Sign of Four” and then afterwards “The Adventures of Sherlock Holmes” which comes out this next month as a book.