Cliffs Notes (if this is what Nacireman is referring to):
The Multitude has a list of (IIRC, 333) doomed planets that they are in the process of destroying.
Earth is on that list.
Turns out that Brainiac was also using that list to get to the doomed planets first to collect and preserve artifacts as well as a city of people from each doomed planet.
Captain Comet has gone off-planet in search of the Planetary Cuckoos who somehow can provide a solution and/or possible defense.
The Multitude is supposedly unstoppable yet when they attacked Krypton, Jor-El somehow repelled them.
In addition, the mysterious Little Man, who put Mxyzptlk in a coma, is amassing an Anti-Superman Army to defeat Superman.
So when this all hits it's going to be non-stop chaos as only Morrison can confuse you with