You can guess what happened next. Uncensored copies have sold for over $2,000 on e-bay.
The New York Times has compared new and old versions. It looks like someone has a fairly broad definition of what would compromise national security. “Another supposed secret removed from the second printing: the location of the Central Intelligence Agency’s training facility — Camp Peary, Va., a fact discoverable from Wikipedia. And the name and abbreviation of the Iranian Revolutionary Guard Corps, routinely mentioned in news articles. And the fact that Sigint means “signals intelligence.””
Read more here.