This is what is posted to Amazon's Operation Dark Heart page:
Important Message for CustomersPerhaps, for transparancy's sake, and to help maintain an informed democracy, Lt. Col Shaffer and St. Martin's Press could publish the book freely and electronically in some format.
On Friday, August 13, 2010, just as St. Martin’s Press was readying its initial shipment of Operation Dark Heart, the Department of Defense expressed concern that its publication could cause damage to U.S. national security. The publication of the initial edition was canceled. However, after consulting with the author, Lt. Col. Anthony Shaffer, St. Martin's Press agreed to incorporate some of the government’s changes, which includes redacting classified text, into a revised edition.