Just started reading book six in the Hitchhikers trilogy and found that you can listen to the original radio series (what got me onto HHGTTG in the first place) for free
radionouspace.net/programs/hitchhikers-guide/
can be downloaded from
www.theoutpost.org/media/hitchhikers-guide-to-the-galaxy-radio-show-audio-mp3/
Always good to put the world and universe into perspective
