Lee Sang-Sul, director at publisher Changbi, said only two other novels since the 1990s had sold more than two million in South Korea, so its a rare achievement for a pure literary work.
Shin last month became the first South Korean to win the 2011 Man Asian Literary Prize with the novel, which portrays a familys guilty soul-searching after the disappearance of their elderly mother.
The book became a million-seller domestically just 10 months after its debut in 2008, and sold more than 100,000 copies in the United States in the first few days after its release there.
It is set to be published in 32 countries. Lee told AFP the publisher plans to print a 10,000-copy special edition with Shins autograph on the cover to celebrate the two-million milestone.The book has won high praise for its illustration of change in a postwar Korean society pursuing urbanisation and economic success, which it weaves into a narrative centered on family and loss.