No pop album has rivalled the Beatles’ Sgt Pepper’s Lonely Hearts Club Band as a mainstream cultural event. As the 40th anniversary of its release (in June) provokes yet another round of applause, that situation seems unlikely to change. Other LPs have sold more copies – Michael Jackson’s Thriller, for one. A few, such as the Sex Pistols’ Never Mind the Bollocks or (What’s the Story) Morning Glory? by Oasis, have soundtracked the time and place of their birth just as memorably. But none casts a spell like the record whose arrival in 1967 ushered in the “summer of love”.

This was the moment when anybody under 25 knew that the value system with which they had grown up was history. Caution, sexual reticence, patient acquisitiveness and all the hallmarks of a decent life, as defined since the Victorian era, suddenly looked bogus. By one of the cosmic strokes of luck that marked their career, the Beatles chose this instant to release an album that straddled the emerging rift. On one hand, Sgt Pepper embraced the tumult of the new, with its swirling psychedelic sound effects, its strangely disconnected stories and a sitar-driven paean to eastern mysticism. In other respects, many of the songs were in love with the past. When I’m Sixty-Four, She’s Leaving Home, Being for the Benefit of Mr Kite and the title track celebrated Britain in the decades before the Beatles and their swinging pals arrived to shake it inside out. A Day in the Life, still most people’s favourite song, contained a bit of both. Add Peter Blake’s iconic cover, and it’s small wonder that such a miraculously inclusive record has endured better than any other of its era.

Rock critics have long argued that Sgt Pepper is not the Beatles’ most musically satisfying LP. Too stylistically diffuse and occasionally self-indulgent in its arrangements, it is generally held to show the group uneasily poised on the brink of fragmentation. Paul McCartney’s more sentimental contributions get a particularly bad press, especially from younger writers nurtured on the fierce rhetoric of 1970s punk.

Enter Clinton Heylin. As he notes, the Beatles meant nothing to him as a child in the 1960s. He is not an obvious candidate to assess a record that captured the spirit of an extraordinary time. He has, nonetheless, assailed the cuttings library with his usual gusto and unappetising tabloid alliterations, and produced a book designed to debunk the shorthand view of Sgt Pepper as “the best album of all time”. This is not as tough a task as it may sound. The album was a farrago of trials and errors that began as a suite of songs about the north and ended up as a “concept” album with no discernible conceptual thread. It took the group and its producer, George Martin, longer to complete than all the Beatles’ other albums put together.

Heylin spends more than half the book comparing Sgt Pepper unfavourably to other records of the same era, such as Pink Floyd’s The Piper at the Gates of Dawn, which played more straightforwardly to the new, acid-frazzled hippie mentality. This misses the point. The Beatles were never the creatures of any “scene”, which is why Sgt Pepper will live on long after all the Heylins have had a go at burying it.

THE ACT YOU’VE KNOWN FOR ALL THESE YEARS: The Life and Afterlife of Sgt Pepper by Clinton Heylin

Canongate £16.99 pp336

Buy the book here for the offer price of £15.29 (including p&p)

Times Recommends

• The Sunday Times 100 best holiday reads
• What will we be reading this summer: the booksellers predict
• Literary festivals: a survivor’s guide