The format of the comic is different from '52', the obvious difference is that it starts from 51 and counts down to 0. The other difference is it's not broken up day by day, which will be a lot easier to read for those that were annoyed by the time stamps. "Week X, Day Y, Hour Z" got old real fast.
On to the issue itself...Countdown #51 opens up with Desaad talking about life and death while Darkseid prepares his game of "chess" with Earth's heroes and villains. Joker's daughter Duela has a run in with Jason Todd (as the Red Hood). Mary Marvel sets out to find Freddy Freeman. The Pied Piper spies on Heat Wave and the Trickster (actually his rat does). Finally, one of the Monitors breaks up Todd's and Duela's party, seems he's out to eliminate the anomalies threatening the Multiverse. Spoilers.
Oh, and a great disaster is coming and only Ray Palmer is the solution.
