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.
OK - those are strong words, and there really has been a lot of great writing in the last 50 years (I did say "possibly"). But the combination of imaginative genius, over-the-top humor and just enough philosophical thought makes H2G2 a true standout. The radio plays predated the published books, and were my first exposure to Douglas Adams in the early 1980s - they remain the best way to experience The Hitchhiker's Guide.
There are only a few audio books that I return to and listen a second time. H2G2 is an audio book that I am moved to listen to at least every two years. Basically, I'd be lost without the Guide... If I could give it six stars, I would.
P.S. Years after I fell in love with the books, I learned that Adams had been a script writer and editor for the BBC's Doctor Who, and that he was a friend of Richard Dawkins - he introduced Lalla Ward (who played Romana on Doctor Who) to Dawkins, they subsequently married. Lalla Ward co-narrates Dawkins' audio books, which I also recommend. That serves to illustrate "the interconnectedness of all all things" (which is something you'll come upon in another of Adams' books - Dirk Gently's Holistic Detective Agency.