An orderly account, meticulously documented, of Holmes’ use of scientific crime detection methods (the Bertillon system, fingerprints, footprints, handwriting and printed document analysis, cryptography) and his familiarity with various sciences. O’Brien persuasively defends Holmes against Isaac Asimov’s disparaging of his chemical knowledge. Many true-crime cases are referenced. An appendix debunks charges that Conan Doyle authored scientific hoaxes, including the Piltdown man. It’s a good job, though too esoteric for anyone not deeply involved with science and Sherlockian studies.