The book "The Idea for Half Kingdom!" - the fourth in the series "Library World 2.0." It's a fascinating read for those who love unexpected guesses, twists and turns of inventive thought. The Spanish grandees and the captive French king, the Russian traveler Sundakov and the French philosopher Michel Montaigne, the ancient Greek hero Achilles and the Beatles and many other characters will meet you on the pages of this book. All of them found themselves in situations where, in order to survive or emerge victorious from the fight, they had to be smart. And they succeeded! The book contains more than 90 acute problem situations. The book is addressed to inquisitive adolescents and adults: parents, teachers seeking to make their lessons interesting, employees of the additional education system.