The Complete Sherlock Holmes

This is the full Conan Doyle canon in one volume: four novels — A Study in Scarlet, The Sign of the Four, The Hound of the Baskervilles, and The Valley of Fear — plus five collections of short stories, The Adventures of Sherlock Holmes, The Memoirs of Sherlock Holmes, The Return of Sherlock Holmes, His Last Bow, and The Case-Book of Sherlock Holmes, fifty-six stories in all.

Read in order, it's also a forty-year record of Doyle changing his mind about the character — he killed Holmes off at the Reichenbach Falls in the Memoirs, was pressured by readers into bringing him back for the Return, and the later stories written into the 1920s have a noticeably different texture from the sharp, compact cases of the 1890s. The short story is the form the character was built for; the novels, especially the first two, feel like Doyle still working out the length he wanted.

As one book, it rewards being read as a whole rather than picked over for the famous cases alone, since the shift in Doyle's own interest in Holmes is part of what's on the page. It's a large, dense volume by nature of what it is — not a book to read cover to cover in a sitting, but a complete reference shelf of the character in one binding.