This is even darker than the Flash volume! Batman isn't the Batman we know and love. He's a much more driven, more morally compromised version. What would happen if a man's child was killed in front of him and he was powerless to prevent it. The Joker is probably even more twisted, and you wouldn't believe me if I told you. That's just the Batman story.
Then there's the story about the biggest jerk in the DC-Verse, Deathstroke, and his crusade to find his lost daughter. I can't call him a hero, because he's not. He's ruthlessly selfish and murderous. I feel bad for anyone who throws in with him. He's not a man I'd trust as far as I could throw him. This is non-stop action, a world in which the seas have become a lawless place of pirates, and the Atlanteans kill humans with impunity.
The story about Dick Grayson and his family tells us how things might have gone if Bruce Wayne had not been there in his life after the death of his parents. Also shows a Europe that has been decimated by the Atlantean-Amazonean war, and where various DC-verse figures have become freedom fighters (even ones who were once villains).
My least favorite was Secret Seven. It was pretty gruesome and twisted, and while I see the point of it all in terms of the Flashpoint story arc, I didn't really appreciate the story at all.
I would still give this four stars because I thought it was pretty interesting, and frankly, nightmarish.