Keith Johnstone is a visionary in the field of improvisation theatre. His concepts of status hierarchies are ground-breaking. They show that humans, like animals, are at ease with each other when the underlying status hierarchy is understood and undisputed.
However, all kinds of interesting tensions are created when the status hierarchy IS disputed. For actors, this concept from Keith's book is golden:
1) If you want to be seen as a natural performer, you need to know your status in relation to the other humans, and even things around you.
2) If you want to create interesting drama, you and your co-actors need to manipulate your statuses in interesting ways. These dynamic movements and challenges are interesting and funny for the audience.
Keith describes this and much, much more in his fascinating book. The generous use of actual improvisation situations makes the book very hands-on, funny and analytical.
Impro also expands from improvisation acting to such areas as creative writing, teaching and mask and trance work. Even the bits one does not agree with are superbly constructed and offer an insightful view on the sometimes weird and wonderful world of creative minds at work.
The improvisation actors in such shows as "Whose line is it anyway?" or London's Comedy Store borrow many of their techniques from Keith.
This book is one to read, whether you are an actor, spectator or just plain interested in smooth, congruent human interactions. Pure genius.