Steven Berkoff wrote his version of Agamemnon but the original author of the story was: Aeschylus an ancient Greek playwright who wrote the story of Agamemnon.
Style of theatre-
“Like smoking, naturalism can damage your health” which sums up Berkoff’s approach to naturalistic theatre. His style is non-naturalistic, often focusing on movement rather that voice. According to him, the only purpose of a script is to help “minimalise and physicalise” the story; stripping it down to its most basic components.
Reference : doesn't share name. "Steven Berkoff Theatre Technique" Blogspot.com. http://dramaandsuch.blogspot.co.uk/2013/02/steven-berkoff-theatre-technique.html?m=1 , 10/02/2013. Web. 11/06/14.The theory of Total Theatre is key to Berkoff and stemmed from Artaud’s theatre style. Total Theatre maintains that every aspect of theatre must have purpose: every movement, that is choreographed; to each line, that is learned perfectly; to each lighting effect, that is used to convey a mood or message; to each sound effect, that enhances the audience’s experience; to each prop that has a use. The aim of Total Theatre is to create extreme moods to give the audience an overwhelming experience and to shock, amuse, scare, or amaze them.
Conclusion - Steven Berkoff didn't necessarily re-write the whole play he just applied his own style of theatre, which is necessary I think with this play because its got such a bold story line and add the exaggerated movements and types of body language you can really make the performance effective to an audience in ways that will engage them and keep them wanting more.