Outside of a masterclass with a Sanford Meisner-type or a Ute Hagen, this well-written, well-crafted book will teach you a tremendous amount in regards to make a character yours with little or no time to prepare. It will give you the skills to leave a lasting impression on casting directors everywhere.
Shurtleff's technique extends to once you have the role as well, preparation required to get the role will also assist you in making the role memorable.
It's also extremely helpful for screenwriters and playwrights, because it should give you insight on how to craft scenes for maximum impact by understanding how actors mine scenes for character, passion and emotion.