burning like matchsticks in the face of the darkness

Was there only one Italian author? I thought there was more than one.

Asimov's Guide to Shakespeare says:

The first version of a play which is specifically that of Romeo and Juliet appeared in a collection of romances, Il Novellino published in Italian in 1476 by Masuccio Salernitano. It was adapted, and in the process, made into something considerably closer to the Shakespearean version (down to the names of the characters) by Luigi da porto in or about 1530.
The first important English version of the story was in the form of a long narrative poem, The Tragical History of Romeus and Juliet, published in 1562 by the English translator Arthur Brooke. It was Brooke's poem that Shakespeare used as his direct source, following it quite closely

Flipping through the volume there doesn't seem to be much information about where he got any other plots from. It does mention that he used Plutarch as a major source for Antony and Cleopatra, Julius Caesar, and a third play, but obviously that's a bit different from using someone else's story for the base of Hamlet or Macbeth.

A quick Gooogle search gets me this (http://www.melicreview.com/archive/iss16/cechaffin.html):

Shakespeare was not original except in his treatments, as he stole his plots from Italian Renaissance romances or English histories (esp. from Holinshead's Chronicles), with a few borrowed Greek and Roman tragedies from secondary sources. Most of his mythology appears directly derived from Ovid, whom he likely read in grammar school. Although he added psychological depth to inherited characters, and created new characters as the dramas demanded, he rarely invented a story, except perhaps The Tempest, for which we lack a principal source. This fact makes me sometimes wonder if Eliot had Shakespeare in mind when he said, "Great artists steal."