Woody Allen said of Lajos Egri "I still think his 'The Art of Dramatic Writing' is the most stimulating and best book on the subject ever written, and I have them all." (Part One, 'Woody Allen - A Biography' by Eric Lax).
This is how I found out about Egri's book and were I to try to give it the full praise it deserves I'd quickly run out of superlatives.
Even if you have no intention of getting into writing I would recommend this work because of the way it will transform your understanding not only of plays, but all narrative art forms. You will put down the book enlightened, empowered and aware of how little many supposed authorities in the field of writing (especially in higher education) grasp about the fundamentals of play-, novel- & screen-writing.
For someone who wants to be a writer this work will prove invaluable. I won't go into the specifics of Egri's approach (which involves the distinction between an idea and a premise and the narrative's role in the 'proving' of premses) since it wouldn't be possible in the space available, but urge you to get a copy now.
Will Taylor