It's already happening. In a few weeks Clinton Heylin, author of previous biographies of Dylan and Van Morrison, releases his book, The Act You've Known For All These Years, to coincide with the very day of the album's official release . . . 1 June 1967. (In fact, the album appeared in shops on 26 May 1967, so it seems apt to get in early, ahead of the deluge. ) For Beatlemaniacs Heylin's book comes at a timely juncture.

It's only a few months since the release of the hugely impressive Love album of Sir George Martin remixes and, more saliently, EMI's recent deal with iTunes to make the Fab Four's back catalogue finally available for legal download. So while Beatles Inc rolls on inexorably, the times, are indeed, a changin'.

Sgt Pepper endures as the greatest album of all time, according to many. It's hard to disagree, even if it could have been oh so different. During that spring of '67 there were three other albums that would have changed the face of music had they been released before Sgt Pepper. One of them did, but in far more subtle ways than might be thought. As recording was in progress in Abbey Road, one Syd Barrett was across the hallway recording an album that would set the template for 1970s prog rock.

Piper At The Gates Of Dawn may always play second fiddle to 1973's Dark Side of the Moon commercially but Piper remains most musicians' favourite and most accomplished Floyd album.

One of the many myths surrounding the recording of Sgt Pepper is well documented by Heylin: Paul was fascinated by the din the Floyd were making and listened in on a number of sessions.

At the same time Brian Wilson's Smile was being recorded as a follow-up to the Beach Boys' 1966 opus Pet Sounds but it was shelved amid tensions between the band. It didn't see the light of day until February 2004 and to this day Pet Sounds remains for many the greatest album of all time. In fact, it came second on Rolling Stone's top 500 albums of all time . . . behind, yes, Sgt Pepper's Lonely Hearts Club Band.

Then there's Dylan, ever the wily observer, who eschewed what he saw as an uneasy competitiveness growing out of the nascent pop culture, and shelved his oft-bootlegged Basement Tapes around the same time. So Sgt Pepper got to stand alone and they've been writing books about it ever since.

It's easy to forget why now but the album as a concept was very much in its infancy in 1967, while record-as-pop-art had never before been conceived. Sgt Pepper changed all that. It featured the first iconic cover, spawning a generation of teenage bedroom posters. By the mid-'70s the imagery had been so inculcated into popular culture that it began to be parodied by the likes of Frank Zappa (only a year later on We're Only In It For The Money) and many others, including the Red Hot Chili Peppers, since. It was also the first to feature lyrics printed on its inner, gatefold, sleeve.

Musically of course, Sgt Pepper stands as the most innovative album made. It just so happened that there was an explosion in recording technology at the end of the decade and the Beatles, who had given up touring to become a studio band, were at the vanguard of that. Heylin goes where few have gone before in his book, even if it is yet another revisionist account of the most written about band in history.

He also slaughters a few sacred cows, particularly Ian MacDonald, whose exhaustive Revolution In The Head has endured as probably the best book written about the Fab Four. Heylin rightly points out that writers such as MacDonald just can't stop themselves from being nostalgic to the point of self-satisfaction. I was there and you weren't so you'll never know. . .

As such, Heylin's tome is research- and interview-based because he wasn't there and he uncovers plenty of facts that Beatles anoraks will love, including the dispute over how 'Lucy In The Sky With Diamonds' was written (did three-year-old Julian really come up with the title? ), that the cover art was originally meant to be a painting of a beach, that it started out as a concept album but Lennon couldn't be arsed when it came to finishing off the last four songs and that it was intended to sound better in mono. And that's just the start of it. It's the album that will never go away. . . .

'The Act You've Known For All These Years' is published on 1 June