Sgt. Pepper’s Lonely Hearts Club Band began as a concept album. It was Paul McCartney’s idea to recreate an Edwardian era army band for the album; this would give the Beatles an alter ego that let them do something different from what the public expected. It would give them the artistic freedom to do other kinds of music from what the Beatle’s had become known for. The original concept was abandoned in the studio in favor of a more experimental approach that kept some of McCartney’s ideas but expanded the range of the record to include songs like George Harrison’s "Within You Without You," inspired by his trips to India to study the sitar and Eastern meditation practices. John Lennon’s “Lucy in the Sky with Diamonds” and other songs were also experimental and used sound in novel ways that marked the band’s departure from performing live and were made possible by using the studio as essentially another musical instrument. The use of sound in this way indicates the influence of the song “Strawberry Fields Forever,” released a few months before Sgt. Pepper’s Lonely Hearts Club Band. Lennon’s song “A Day in the Life” (with a bridge by McCartney) closed the album on a striking avant-garde note. Today’s pop music fans have little understanding of just how revolutionary and unexpected this song was back in 1967. You had to be there. But we can also say that its moment lives on; It was a milestone in the history of vinyl recording and 50 years later its cultural influence lives on.

Rolling Stone writer Langdon Winner defined its significance this way: “The closest Western Civilization has come to unity since the Congress of Vienna in 1815 was the week the Sgt. Pepper album was released. In every city in Europe and America, the radio stations played [it] ... and everyone listened ... it was the most amazing thing I've ever heard. For a brief while, the irreparable fragmented consciousness of the West was unified, at least in the minds of the young.” Sgt. Pepper quickly became closely identified with the Haight-Ashbury’s 1967 "Summer of Love. Musicologist Tim Riley said the album "drew people together through the common experience of pop on a larger scale than ever before."

American radio stations dropped their regular programming to play the LP from beginning to end virtually non-stop. It was number one on the US Billboard album chart from 1 July to 13 October 1967. It sold 2.5 million copies in the first three months after it was released. It outsold all the previous albums of Beatle’s career.

According to Robert Christgau, the “Dean of American Rock Critics” it was more a break with the past than a major breakthrough and said, "Although Sgt. Pepper is thought of as the most influential of all rock masterpieces, it is really only the most famous. In retrospect, it seems peculiarly apollonian – precise, controlled, even stiff – and it is clearly peripheral to the rock mainstream."

In a mocking appraisal of SPLHCB written just before its 40th anniversary in 2007, critic Richard Smith of the British newspaper the Guardian pointedly stated that "if not the worst, then certainly the most overrated album of all time." He also called it an "excruciating" LP that was overvalued for its cultural impact by music writers and "not because of anything intrinsically great about the record" as much as its importance in the history of music. In 2007, when he was asked name a "supposedly great" album he would "gladly never hear again", artist/writer Billy Childish said the album "signaled the death of rock 'n' roll." As recently as 2015, Rolling Stones guitarist Keith Richards criticized the LP as "a mishmash of rubbish, kind of like Satanic Majesties," naming a Stones record issued in the same era.

Lester Bangs, known as the "godfather of punk rock journalism,” noted back in 1981 that "In the 60s, rock and roll began to think of itself as an 'art form'. Rock and roll is not an 'art form'; rock and roll is a raw wail from the bottom of the guts."

The musicologist John Kimsey cites the preservation of authenticity as a guiding tenet of rock music and suggests that many purists denounce Sgt. Pepper in that respect, accusing the album of "mark[ing] a fall from primal grace into pretense, production, and self-consciousness." George Martin, along with Brian Wilson, is generally credited with helping to popularize the idea of the recording studio as a musical instrument which could then be used to aid the process of composition. In MacFarlane's opinion, Sgt. Pepper's most important musical innovation is its "integration of recording technology into the compositional process." The musician and producer Alan Parsons believes that with Sgt. Pepper "people then started thinking that you could spend a year making an album and they began to consider an album as a sound composition and not just a musical composition. The idea was gradually forming of a record being a performance in its own right and not just a reproduction of a live performance."

But earlier, in a particularly influential opinion, the New Statesman's revered classical music critic Wilfrid Mellers praised its elevation of pop music to the level of fine art. Paul McCartney was awed by the album’s reception: "The curtains flew back and [Jimi Hendrix] came walking forward playing ‘Sgt. Pepper'. It's a pretty major compliment in anyone's book. I put that down as one of the great honors of my career."

David Crosby of the Byrds, who had become a close friend of the Beatles, was at one of the recording sessions for the album and was overwhelmed by what he saw and heard: "I was, as near as I know, the first human being besides them and George Martin and the engineers to hear 'A Day in the Life,'" Crosby recalled in an interview with Filter. "I was high as a kite – so high I was hunting geese with a rake. They sat me down; they had huge speakers, like coffins with wheels, that they rolled up on either side of the stool. By the time it got to the end of that piano chord, man, my brains were on the floor."

Now, in 2017, The Beatles organization has delivered an expanded 50th-anniversary edition of Sgt. Pepper’s Lonely Hearts Club Band. Songs and outtakes not included in the album originally show up in many forms in the deluxe edition, echoing the treatment of Bob Dylan’s many official “bootleg” albums that do the same thing.

Several configurations are accessible on the upcoming release--a two-CD Deluxe Edition, a Deluxe vinyl version, as well as a 4-CD/DVD/Blu-ray Super Deluxe boxed set. The first disc contains a new stereo mix of the original LP, produced by Giles Martin, the son of George Martin, the late Beatles producer, sometimes called the fifth Beatle.

The boxed set includes 5.1 surround audio, and a 144-page hardcover book full of photos, and recollections from some of the participants in the recordings. Unfortunately, there is nothing to be seen of the legendary “Carnival of Light,” the “holy grail of lost Beatles recordings.”

In March 2013, a copy of Sgt. Pepper’s signed by all four Beatles sold at Heritage Auctions to an unidentified buyer for a record $290,500. There can remain no doubt that similar deluxe sets will be released in coming decades. The Beatles will be with us for a very long time.