When was the first audio book recorded?

Caedmon started recording audio files of great authors and poets of the 1950's. He started recording these files as far back as 50 years ago! The recordings might not have been as entertaining as the audio recording we have today, but those early recordings can arguably be defined as the first audio books. Also, as a little side note, the transition of these book recordings into audio cassette tapes didn't happen until the late 1970s up to the 1980s and the audio book phenomenon didn't really kick off until the mid to late 1990s.