The adventures of Sherlock Holmes, by Sir Arthur Conan Doyle

I again return to an old favorite. Dr. Watson documents the amazing deductive powers of Sherlock Holmes in this collection of short stories.
Three audio versions are available for free from Librivox.
The text version is available for free from Project Gutenberg in Kindle, EPUB and other formats.
audio: approximately 10 hours
text: 240 pages