Brain on a plate.
This record most perfectly demonstrates Maiden's contemporaneous brilliance and idiocy. The music totally slays, but they seem determined to thoroughly exhaust their dull 'Piece of Mind' pun. First, on the cover, Eddie's chained up, in a straitjacket, and has a head wound repaired with a couple of screws, meant to inform you that his brain has been taken outta there. Lost his mind, you know. Then you flip the record over, and there's a verse from 'Revelations':
And God shall wipe away all tears from
their eyes; and there shall be no more
Death. Neither sorrow, nor crying.
Neither shall there be any more Brain;
for the former things are passed away now.
In the context of that familiar Maiden artwork, this verse seems unnecessary, but it's not totally out of place. The art's scary, the music is heavy, we're all gonna die and lose our brains, whatever. But then you slide the record out of the sleeve and see they haven't done anything violent or awesome with Eddie's brain, they just stuck it on a plate with boiled cauliflower and baby carrots. That's it, man. Brain on a plate.
This was also the first record Nicko McBrain recorded with the band, kind of a fortuitous occurrence, keeping your focus on the 'brain' theme and helping the band impress the idea of mind loss onto the very mind you're doomed to lose.