Beginning with (roughly) Help!, and culminating with (roughly) Revolver, The Beatles' middle era is my favorite. These recordings still exude the air of camaraderie and light-hearted playfulness of their early recordings, but it is balanced with the musical sophistication of their later works, and some hints of the psychedelic influences that would eventually come to fruition. It is really the era where all of their strongest aspects are at work at the same time. While I enjoy all of the music from this period, Revolver is unquestionably the pinnacle of not only their career, but one of the best albums ever laid to tape.
The artwork was created by Klaus Voorman, an old friend of the band. The blending of ink drawings and photographs of the band was incredibly groundbreaking in its time, and this unique piece of pop art on the cover must have drawn quite a few eyes in record stores and helped add to the already significant sales of the album.