Was and possibly still is, the best selling 12" single of all time, in the UK.
I bought it from WHSmith (I had to order it specially).
It came in a black sleeve, mocked-up like one of the old floppy disc - some examples here..
http://images.google.com/images?q=blue monday sleeve&um=1&ie=UTF-8&sa=N&tab=wi
I remember that the one I got, had the 'A' and 'B' side labels on the wrong way around.
I've read interviews with the band, who say that they now dislike the song, because they felt that it has become something of a novelty record.
BTW: The '88 remix was shite... as was the video for it.
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Well let me first warn you that most of the 80s music I like is gay.
In the case of the Bangles, might I suggest 'Lesbian'.
From memory, I can't remember any of them being particularly shaggable.