Genesis' greatest work, and perhaps the best thing to come out of the Prog genre, despite a complete nonsense "plot," this record manages to hang together beautifully over four sides of vinyl, a feat not equalled by any of their contemporaries; many tried the double concept album, no one else succeeded in creating something worth listening to all the way through.
The key to this feat was the band's intense focus on SONGS (fancy that), not epic monstrosities (Jon anderson, I'm looking at you here), and tight production. Sure, there are bleeps and bloops and weirdy beardy noisy things going on here and there, but this is no Van der Graaf generator LP. The music is beautiful, and the lyrics, though patently silly (a sin of which pretty much everyone at the time was guilty), are very evocative and contain such gems as "Erogenous zones I love you!" Ranging from Beatles-derived pop to the far reaches of Progressiveness (for want of a better term), the tracks strike a wonderful balance of styles and give the ear more than a few hooks on which to hang its hat. Like "2112" for Rush or "Fragile" for Yes, "The Lamb Lies Down on Broadway" is the pure unalloyed refined essence of its creators. You really should buy it.