Mysterious books bring 'Great Controversy' to Chicago mailboxes

More than 600,000 copies of a mysterious book have made their way to Chicago mailboxes.

Residents have had varying reactions to "The Great Controversy," a 377-page paperback that features lessons on Christianity, freedom of religion and moral reasoning.

The book was authored by E.G. White, a founder of the Seventh-day Adventist Church, in the 1800s and was sent specific Chicago zip codes because of the city's reputation of violence.

However, Chicago isn't the only one to be flooded by the enigmatic paperbacks.

The books have also been sent in massive numbers to New York City, Philadelphia, Washington D.C. and Charlotte, North Carolina.