U2's decision to choose Brian Eno as producer for their new album was a bold move.

Clearly conceived as a challenge for the band – and indeed for Eno who by his own admission was largely unfamiliar with the band's work prior to this – it gave credence to Bono's post-Phoenix Park declaration that that memorable concert had brought to a close the first full cycle of U2.

Further emphasising, after three acclaimed studio albums and a live wrap-up souvenir, that U2 had arrived at a radical point of departure, was Eno's playful but pointed assertion in his interview with Bill Graham one month ago, that the album would introduce 'five or six new U2's' to the world.

All of which means that The Unforgettable Fire has a lot to live up to – and it's this listener's verdict that it does so, unequivocally.

Inspired by the life of Martin Luther King, the single 'Pride (In The Name Of Love') is a characteristically soaring and uplifting tribute to those who fight for peace and justice. Eminently deserving of its chart success where it shames the transparent piffle that clutters up much of the hit parade these days, it is, in the context of the album, the sole surviving variation on the band's most familiar modus operandi. For the remainder of this journey, existing map co-ordinates are of little immediate relevance.

The opening track 'A Sort Of Homecoming' rings the changes loud and clear. The primary colours of yore are here absorbed into a much broader canvas, the totality almost symphonic in its orchestration of sounds (as distinctly opposed to instruments) but without any unnecessary grandiosity that description might imply. There's a subtle but effective Irish undercurrent in both the melody and lyrics while the "O-come-way, o-come-way" refrain effectively evokes the chorus of 'I Will Follow'. And it's true, U2 have come a long way.

One of the most significant aspects of The Unforgettable Fire is the maturing of Bono's abilities as a lyric writer and singer. Throughout the album his choice of language and use of imagery is rich and imaginative, at times brilliantly so, as in 'Promenade', a beautifully embellished love song, that's both spiritual and sensual, and wherein Bono echoes Van Morrison in the line 'up the spiral staircase to he higher ground'.

And then there's the title-track, possibly the album's shining achievement. The visceral string arrangement scored by Noel Kelehan is superb, as is Bono's vocal, including a perfectly integrated falsetto, replete with melodic passages of genuine beauty. The Unforgettable Fire brings the band into a different dimension in terms of dynamics, texture and atmosphere.

If U2 tended on occasion towards stridency in the past, that fault has been eradicated here. 'Wire', a frenetic black and blue executioner's song is abrasive but not bruising, while 'Bad' and 'Indian Summer Sky' eschew the temptations of the anthemic in favour of controlled developments of the music's intrinsic power.

I'm still wrestling with the strange 'Elvis Presley And America', in which at one point Bono's treated voice sounds uncannily like Lou Reed and thus far, only '4th Of July', an instrumental that's akin to a slow-motion fireworks display, leaves me cold.

'The Unforgettable Fire' ends with 'MLK', again addressed to martin Luther King. Part elegy, part Lullaby, it closes U2's warmest album yet on an appropriately direct and moving note.

This then, is the beginning of the new chapter of U2. With an album as rich and rewarding as The Unforgettable Fire as a introduction, the possibilities for the future seem limitless.