Arthur is drawing a parallel between the full immersion experience of the Sens-O-Tape recording and 70mm wide-screen motion pictures with six track sound recording, a recording system which was state of the art in 1979.
As an answer to "the meaning to life, the universe and everything", this has sparked a great deal of speculation over the years.
Douglas Adams had this to say about it:
"The answer to this is very simple. It was a joke. It had to be a number, an ordinary, smallish number, and I chose that one. Binary representations, base thirteen, Tibetan monks are all complete nonsense. I sat at my desk, stared into the garden and thought '42 will do.' I typed it out. End of story."
This is a reference to a series of famous British Second World War propaganda posters, exhorting the public not to discuss sensitive information about the war effort in public.
A line from the song Blowin' in the Wind by Bob Dylan.
The Restaurant at the End of the Universe is the title of the next book in the Hitchhiker's series.