Kenneth Muir 
Sources of Shakespeare’s Plays [PDF ebook] 

First published in 1977. This book ascertains what sources Shakespeare used for the plots of his plays and discusses the use he made of them; and secondly illustrates how his general reading is woven into the texture of his work. Few Elizabethan dramatists took such pains as Shakespeare in the collection of source-material. Frequently the sources were apparently incompatible, but Shakespeare’s ability to combine a chronicle play, one or two prose chronicles, two poems and a pastoral romance without any sense of incongruity, was masterly. The plays are examined in approximately chronological order and Shakespeare’s developing skill becomes evident.