German native Daniel Domscheit-Berg, also known as Daniel Schmitt, was the former right-hand man of the website's embattled founder, Julian Assange, whose mission is to publish previously undisclosed or classified documents. But Schmitt quit in September over disagreements about the management of Wikileaks.
Crown said it expects to publish "Inside Wikileaks: My Time with Julian Assange at the World's Most Dangerous Website," on February 15, in the United States and 13 other countries.
"In his book, (Schmitt) will reveal the evolution, finances, and inner tensions of the whistleblower organization, beginning with his first meeting with Assange in December 2007," said Crown, a unit of Bertelsmann AG's Random House.
WikiLeaks has been the center of controversy in the U.S. government and around the world in recent weeks following its release of classified diplomatic cables and other communication that portrayed U.S. and other world leaders in a negative way.
Assange was arrested in Britain and held on a request by the Swedish government for him to return to that country to face questioning in a sexual assault case. He is currently free on bail and living in a private house outside London.