Audiobooks have literally changed my life. I now actually ENJOY doing mindless chores because they give me plenty of listening time!
The Hitchhiker's Guide to the Galaxy was the first radio comedy show to be recorded in stereophonic sound and it was acted out by a full cast of professional actors, but what really sets this show apart is the sound effects which were completely innovative at the time. "One of Adams's stated goals was to be experimental in the use of sound. Being a fan of Pink Floyd and The Beatles (and especially the experimental concept albums both bands produced in the late 1960s and early 1970s), Adams wanted the programme to have the feel of a "rock album...to convey the idea that you actually were on a spaceship or an alien planet — that sense of a huge aural landscape". (From Wikipedia)
Of course today, there is a quaint quality to those sound effects, but that only adds to the overall charm of the experience. I first discovered this show in the late 80s when a local radio station aired the series, and must say that more than 20 years later, a reading of the book (which not surprisingly seemed awfully flat) it felt just as fresh, off the wall and yes, innovative as it did the first time around.