This is the second half and the conclusion of the Justie League: Generation Lost storyline which has been a great ride from start to finish.
You don't need the Brightest Day storyline at all. The only connection to Brightest Day was Max Lord's Mission from the White Lantern and it was only a minor subplot that was handled inside these issues.
In the Brightest Day main storyline his mission is barely even mentioned or what he did to assigned and that he succeeded in his mission, which you also see in this mini. If any thing the Brightest Day storyline needs these issues to make that storyline feel complete.
You do need Vol 1 which I also reviewed(link).
Judd Winick did a awesome job...with this storyline and I'm not sure how much of the plot belongs to Keith Giffen, but Giffen is a master story teller that gave Winick an awesome story to tell. The story revolves around the defunct Justice League International which was a series that Keith Giffen was the main writer.
YEA!...Batman shows up, in issue 22 of the series. I do love Batman. What's even better is that he doesn't steal the show. He was part of the original Justice League International, so it was great to have him on board.
Winick didn't let him steal the essence of the story away from the characters that started it. In the end, it was the team that started the series that resolved it, and that's how a story should wrap up.
This was a great read.
Justice League : Generation Lost Vol 2 Brightest Day
Writer : Judd Winick
Pencils: Joe Bennett, Aaron Lopresti, Fernando Dagnino
Inks: Jack Jadson & Ruy Jose, Matt Ryan, Raul Fernandez
Letters: Sal Cipriano, Swands, John J Hill
Covers: Cliff Chiang, Dustin Nguyen, Kevin Maguire, Aaron Lopresti
Editors: Rex Ogle & Brian Cunningham