Although Sir Arthur Conan Doyle would have preferred to be known for his historical fiction, or perhaps even his sci-fi, it is for Sherlock Holmes that he is most remembered. Created between 1887 and 1927 in 62 cases (4 novels and 58 short stories), Holmes is a private detective with powerful observation and deduction abilities.

Doyle was quite a prolific author, writing more than 300 fictional stories (including 24 novels) in all genres like history, fantasy, adventure, science-fiction, crime, drama, war. . . plus more than 1200 other works such as essays, pamphlets, articles, letters to the press, poems, interviews, plays. . .on so many subjects—such as politics, spiritualism, war, crimes, etc. (see a list of his Complete Works). Though Sherlock Holmes was certainly his most popular character, Doyle thought that Holmes was obscuring the rest of his works, so he decided to kill him off in 1893 at the end of the 26th story, "The Adventure of the Final Problem" (included in Memoirs of Sherlock Holmes). However, eight years later, succumbing to family and editor pressure, he "resurrected" the detective and ended up writing 34 more stories between 1901 and 1927.

While these are murder mysteries, they're generally suitable for fairly young readers, including some pre-teen avid readers who aren't too sensitive. The violence isn't graphic, and there is no sexual content other than allusions to extra-marital affairs. Holmes' cocaine/opium use is sometimes brought up as a concern, as is negative mentions of the Mormons and occasional period-typical racism/classicism in the books. Some people complain that they find certain titles slow going (like Hound of the Baskervilles), but this is by no means the most common opinion. 

As the Sherlock Holmes novels and story collections were written over the course of forty years, and later gathered into books, the sequence is not entirely sequential, but these nine volumes gather all the stories in (mostly) chronological order, though not in the order they were published:

(PG = Project Gutenberg, LV = Librivox recordings (we've usually chosen narrator David Clarke)

1. A Study in Scarlet - PG | LV
   (novel originally published November 1887 in Beeton's Christmas Annual)
2. The Adventures of Sherlock Holmes - PG | LV
   (stories published 1891–1892 in The Strand)
3. The Sign of the Four - PG | LV
   (novel originally published February 1890 in Lippincott's Monthly Magazine)
4. The Casebook of Sherlock Holmes - PG | LV (read by Thomas A. Copeland)
   (stories published 1921–1927)
5. The Valley of Fear - PG | LV
   (novel originally serialized 1914–1915 in The Strand)
6. The Memoirs of Sherlock Holmes - PG | LV
   (stories published 1892–1893 in The Strand)
7. The Return of Sherlock Holmes - PG | LV
   (stories published 1903–1904 in The Strand)
8. The Hound of the Baskervilles - PG | LV
   (novel originally serialized 1901–1902 in The Strand)
9. His Last Bow: Some Later Reminiscences of Sherlock Holmes - PG | LV
   (stories published 1908–1917)

Holmes has inspired an enormous number of plays, films, knock-offs, spin-offs, and other fan fiction. Some of these try to fill in gaps in the Holmes chronology and give him adventures in other lands, for example Sherlock Holmes and the Red Demon in America and the Mandala of Sherlock Holmes in India & Tibet (there are many others). But it wasn't until 2011 that the Doyle estate authorized another novel, by acclaimed author Anthony Horowitz. This one, called House of Silk, was well-received and followed up in 2014 with Moriarty (we don't recommend these for pre-teens, though).

There have been many editions of the Sherlock Holmes stories published over the years, and our goal is always to offer a good variety of quality editions. That said, we'll offer any attractive used copy that comes our way. But what about new editions? We've decided to primarily recommend the Seawolf collection of the books, because they're handsome, legible, illustrated, and affordable, available in hard or softcover, they include all the novels and stories, and Seawolf also publishes other matching novels by Doyle. (We have one quibble with an editorial issue in the story "Resident Patient" in Memoirs of Sherlock Holmes, but it's a minor one.) 

We've researched a number of others, but most other attractive sets are either out of print, unavailable to us, missing stories, or not illustrated. These include the Arcturus, Wordsworth, Headline and Oxford boxed sets and various collections from Penguin and others. Our favorite is the Norton Annotated Sherlock Holmes 3-volume set (though the volumes are unwieldy), and will carry them if they're ever available again. If you have any suggestions, we'd be glad to hear them!