"The Case Book of Sherlock Holmes is the final set of twelve (out of a total of fifty-six) Sherlock Holmes short stories by Arthur Conan Doyle first published in the Strand Magazine between October 1921 and April 1927.
The first British edition and the first American edition of the collection were both published in June 1927. However, they had slightly different titles. The title of the British collection was The Case-Book of Sherlock Holmes (hyphenated ""Case-Book""), whereas the title of the American edition was The Case Book of Sherlock Holmes (""Case Book"" as two words).
Further confusing the issue of the title, some later publishers released the collection under the title The Casebook of Sherlock Holmes (""Casebook"" as a single word). "