One of McCartney's aunts reportedly requested that he write a song with some other theme than boy-girl relationships. British disc jockey Jimmy Savile claimed that McCartney's inspiration came from seeing drummer Ringo Starr reading a book. "He took one look and announced that he would write a song about a book," he said.

The song's lyric is in the form of a letter from an aspiring author addressed to a publisher. The author badly needs a job and has written a paperback version of a book by a "man named Lear." This is a reference to the Victorian painter Edward Lear, who wrote nonsense poems and songs of which John Lennon was very fond (though Lear never wrote novels). The Daily Mail was Lennon's regular newspaper and was often in the studio when The Beatles were writing songs.

Aside from deviating from the subject of love, McCartney had it in mind to write a song with a melody backed by a single, static chord. "John and I would like to do songs with just one note like 'Long Tall Sally.' We got near it in 'The Word.'" He also claimed to have barely failed to achieve this goal with "Paperback Writer," as the verse remains on G until the end, at which point it pauses on C. The backing vocals during this section are from the French children's song "Frère Jacques".

British Science Fiction writer and Humanitarian Douglas Adams was very fond of this song, to the point of having it played at his funeral.