Before hitting the play button, clear your head, glance at the glum Anton Corbijn photos and try to remember the splash this album made in 1987.

The 1980s had plenty of good music, but little of it was in the charts. You had to dig for it. This is four years before alternative music turned a serious dollar. Then came the clamouring Joshua Tree.

It's easy to sneer at U2's play for the stadiums - the big sound, the theatrics of Bono (below, left, with bassist Adam Clayton), the references to American music from a band that had always sworn off blues and rock cliches.

And yet U2 were forcing the mainstream to come to their songs about Argentina's 'mothers of the disappeared', heroin addiction and a US-backed insurgency in El Salvador. They arguably succeeded in feeding more artistry into the cashed-up end of pop culture than any album had since Sergeant Pepper 20 years earlier.

U2 spent their career working towards Joshua Tree and by running away from it since then they've earned a spot in the pop pantheon. Journalist Bill Flanagan writes in the liner notes for this package: 'Some bands get to the top of the mountain and come back down. Some fight to stay there. U2 got to the top of the mountain and used it as a place to build a launching pad.'

Guitarist The Edge describes a two-week effort after recording the album when U2 produced 'a set of B sides that is without doubt the finest U2 work ever not to be included in an album'. All those tracks are in this package, along with the band accompanying Allen Ginsberg as he reads his poem America.