Reviewed by Ian MacDonald, in Revolution in the Head:

The Beatles' twelfth British single was their first since SHE LOVES YOU not to go straight to No. 1 in the UK. Written by McCartney – the second of a run of three consecutive A-sides by him – it strained too hard to define a new style for the group, its air of contrivance sounding flashy after the ideal balance of form and feeling in WE CAN WORK IT OUT. Displaying The Beatles' cannabis-induced fascination with getting the maximum out of one chord, PAPERBACK WRITER offers a jokey lyric reflecting its era of classless ambition: the generation of 'young meteors' who in the mid-Sixties rose from provincial and working-class backgrounds to dazzle the heights of British fashion, film, and print [1]. Beyond this social observation any potential poignancy is sacrificed to excitement, word-games, and studio-effects. In the end, this is a record less about its time and place than about pop records in early 1966. Intermittently glimpsed in The Beatles' music, 'Swinging London' was less interesting to them as visiting northerners than it was to cynical locals like The Kinks and The Rolling Stones [2].

Now living within walking distance of Abbey Road (in Cavendish Avenue, St John's Wood), McCartney was often at the studio before the others, trying out musical ideas and production effects which he then presented to them as faits accomplis. While the group benefited immensely from his energetic attention to detail, it didn't make him popular and his pedantic insistence on Harrison playing every guitar line just so often caused tension. (Whether he or Harrison recorded the guitar riff on PAPERBACK WRITER is unknown, though it's clearly McCartney's idea – based, as Lennon later remarked, on the similar figure in DAY TRIPPER [3].)

Made in eleven hours, the track has a widely divided stereo image using, among other novelties, a drum part channelled separately across the spectrum (snare and cymbals left, tom-toms centre, bass-drum right). For his prominent high-register bass part, McCartney swapped his Hofner for the long-scale Rickenbacker, a guitar with a solid, cutting treble tone which he modified by miking his amp through a second speaker and rolling off the top with compression to get a smoother sound [4]. With a tape-echoed chorus, the vocal arrangement includes passages of four-part polyphony modelled on The Beach Boys, whose 'Sloop John B' had just entered the UK charts. That Lennon and Harrison were not entirely serious in performing their falsetto parts can be heard in the gasps of laughter audible on a very 'dirty' vocal track (and the fact that, during the second verse/chorus, they are chanting 'Frère Jacques').

Notes:

1. Salewicz suggests that the subject occurred to McCartney while helping The Beatles' friend John Dunbar catalogue the stock of his Indica book shop in Southampton Row. English culture of this period benefited immensely from the patronage of Jenny Lee, Harold Wilson's Minister for the Arts. Under her direction, theatres, concert halls, galleries, and libraries received vital funding while the Arts Council, chaired by Lord Goodman, gained new grant-giving powers and expanded financial resources. In this atmosphere, creativity flourished in every walk of cultural life.
2. E.g., The Kinks: Face To Face (October 1966); Something Else (September 1967); The Rolling Stones: Aftermath (April 1966); Between The Buttons (January 1967).
3. During one take, McCartney moved to lead guitar, playing the riff with his Epiphone Casino while Harrison took up a short-scale Burns Nu-Sonic bass. Otherwise, Harrison played a Gibson SG Standard and Lennon a hollow-bodied Gretsch Nashville (their respective guitars for RAIN, too, and most of Revolver).
4. Microphones and speakers walk by opposite principles: air-movement to electrical impulse (or vice versa). McCartney's bass amp made the sound-wave which, vibrating the cone of the second speaker, transduced voltage in its moving coil, creating a second signal. This was presumably done for colouration rather than signal boosting. (The larger the second speaker, the lower the available frequencies.)