But if reviews came out before all the reveals of characters etc, wouldn't that ruin revealing them? I'm sure any review would be full of spoilers about the story, right?
Well, the more the release date approaches, the higher chances are that the various webzines and magazines will be invited to what I assume will be closely guarded listening sessions. Usually in those listening sessions you have a pen and a paper to write your impressions and you listen the album once, so those reviewers will focus on the music instead, the story will be complex and difficult to grasp at first.
Back in 1999 the internet was not so massive and I remember the famous "veil of secrecy" about SFAM, but I don't think anyone who heard the album beforehand only once came out and said "Omg there's this long heavy song which is a newspaper article but it's really all made up by the real assassin!"