Young's gargantuan piano composition, lasting more than 5 hours, is something of a patience tester. However, give it the time it needs and you will discover inside it's many aspects a world of new harmonies and sounds. If you've got some serious paper sorting to do or plan on reading for a l o n g time, stick this one and see where it takes you.
This is a great recording, however the (much shorter) version from Day of Gammadon has a particularly great tone to the piano. This one is far less percussive.
I remember having to listen to this for A Level music at school. We didn't know how lucky we were.