You've seen it right, the title is in CAPITAL LETTERS, this book deserves the added exclamation. If you want to know more about how to improve your writing craft, be it playwright, writing a short story, a novelette, a novel, a screenplay, even your grocery-list, buy this book.
Lajos Egri explains the need of having a premise, characters, and conflict to shape the story. He shows that without this the story will not reach its full potential. He proves his points with explanations, and examples of existing plays (from the era he wrote the book), and a session of question that he answers in great detail.
This book helped me understand why some of what I wrote previously worked and some not so much. It gave me understanding where previously I was guessing and going by feeling. It's not that you can't write a great book based on going just with pure imagination, but it's rare. Knowing why things work gives you that much more confidence in your writing, and the right tools to knowingly write (or attempt to) a great book.
I'm glad I read this book. It's a shame I forgot who recommended The Art of Dramatic Writing to me, I would kiss him or her a thousands times. It's a great book and an asset to every writers bookcase.