In 'the blacklist full story', the blacklist is the most obvious key element. It's a compilation of criminals that the story revolves around. Raymond Reddington is another vital part. His knowledge of the criminal world and his ability to manipulate situations are central to the narrative. The FBI's involvement is also key. They are constantly in a power struggle with Reddington, trying to use his knowledge while also controlling him. And finally, the mystery surrounding Reddington's past and his connection to Elizabeth Keen are elements that keep the story going and the audience guessing.
One key element is Raymond Reddington himself. His character drives the story. Another is the blacklist, of course. It's the core concept that sets up the plot for each episode as different criminals from the list are targeted. Also, the relationship between Reddington and the FBI, especially Elizabeth Keen, is crucial.