What is the significance of the Russian Roulette?

The title of the book is a reference to scenes in the movie The Deer Hunter starring Robert De Niro. In this movie, De Niro plays a traumatized Vietnam veteran who was forced to play games of Russian Roulette by his Viet Cong captors. Russian Roulette acts as a metaphor for the inescapable and utterly random chaos of war.
One of the lead characters in the book, George, is nicknamed De Niro. He and his friends are obsessed with The Deer Hunter, and identify strongly with the film's damaged, mentally-scarred characters. He also plays Russian Roulette with his friend Bassam on a couple of occasions. More generally, the randomness, violence and death associated with the deadly game comes to epitomise the daily struggle of young men amidst the ruins of war-torn Beirut. Life itself, like Russian Roulette, has become a potentially lethal game of chance in which one can die at any moment. Reckless gunplay is a way for these young men to deal with the horrors of a hopeless, soul-destroying existence in a city wracked by a seemingly endless conflict.