Probably the most avant garde, adventurous work ever released by a major label, this is a mind expanding, terrifying album.  From the epic Cambridge 1969 (running a wonderfully epic 26 1/2 minutes), the creepy No Bed for Beatle John, and the John Cage tribute Two Minutes Silence (it is NOT the best song on the album because Yoko shuts up, as some reviewers have said), it's an album you are not likely to forget.  Reportedly, it was made after Yoko's miscarriage, accounting for the agony.  The stuff that nightmares and pain are made of.  Yoko's vocals on this album are some of her best work.  John's distorted guitar compliments them superbly (especially on Cambridge 1969).  This is the best of the "Unfinished Music" albums (Two Virgins and Wedding Album being the other two).