Interestingly informative book about Arthur Conan Doyle's creation of the Sherlock Holmes character, drawing from childhood inspirations (perhaps Dr. Watson was named after someone that had attended a school here or for the name of this other person there) and his adult life - specifically, the practice of doctors at the University of Edinburgh, notably, Dr. Joseph Bell, using physical clues to 'deduce' facts about their patients. A lot of comparisons are rightfully drawn between Dr. Bell and Sherlock Holmes, including the emphasis that while the 'science of deduction' seemed magical, "such assessments required educated scrutiny but not second sight."
The book also goes into the history and increasing popularity of the 'science of deduction' and pokes at the fact that deduction is the wrong word entirely for the line of logic that Sherlock Holmes uses. The history and influence of the crime genre in literature, going from sensationalism to thriller and eventually leading to series featured around singular detective characters, is also examined. A lot of name-dropping happens for books and authors that I had barely or never heard of, or the books that I knew them to be famous for were not the ones that the 19th century reader knew well.
Overall, it was well-researched, but the chronology was a bit skewed and the writing tended to end on a tangent and pick up on a completely different topic's tangent from a chapter ago. I did not read it all in one shot so it did not bother me.