Look, if this story is true, releasing it to the press was an intelligence disaster. Sure, the book might help decode some old messages but the key to stopping attacks is the ability to read _future_ ones. If this code book story is genuine, the terrorists will quickly switch to an alternate code system, making decoding future messages all the more difficult.

To illustrate the point, in WWII, a German submarine was captured by the Royal Navy in 1942. The sub crew abandoned the sub and tried to set the scuttling charges to sink it. A very brave British officer boarded the sub. One of the first things he recovered was the German Naval Enigma machine and code books. This was kept highly secret for the obvious reason - the British wanted to be able to read the coded German messages. This event was a turning point in the Battle of the Atlantic and helped break the back of the U-boats. Could you imagine the outcome had the British been foolish enough to broadcast the fact they could read German messages? Before this event, German U-boats were sinking transport ships faster than they could be built. Afterwards, the number of U-boats sank went way up and the number of Allied ships sank went way down.