Flashpoint is a huge event, spanning 65 issues in all, and completely changing the DCU. The substantiated rumor is that Flashpoint is the in-story cause of the relaunch / reboot of the entire DC line coming in September. But for now, it's just good reads.
In a nutshell, The Flash and Booster Gold separately find themselves in a completely different world...only to discover that it's not a different world...it's the same world with a completely different history. I don't want to spoil it too much, but it has a bit of the flavor of AoA...only better, IMO.
A few enticing tidbits:
Bruce Wayne was killed. Thomas Wayne survived.
There never was a Flash. At all.
Hal Jordan never got the ring.
Aquaman and Wonder Woman are at war...and have destroyed most of Europe.
Captain Cold is the hero of Central City.
Anyone reading it?