The eldest son of North Korea's late leader Kim Jong-il has predicted the regime would soon fail, with or without reforms, according to a new book that the author says is based on emails and interviews with Kim Jong-nam.

The book says that Kim Jong-nam – who has never met the new leader, his half-brother Kim Jong-un – described the dynastic succession as "a joke to the outside world", and said even his father had originally opposed the hereditary transfer of power.

"The Kim Jong-un regime will not last long," Kim Jong-nam is said to have written, forecasting a power struggle. "Without reforms, North Korea will collapse, and when such changes take place, the regime will collapse."...