OK, I haven't been on the DC side for ages and I haven't touched Justice League since No Justice.
I mostly decided to pick up this issue because I wasn't even aware that Mera was on the team when I saw the cover. Imagine opening the book and seeing that Synder brought back Starman. Plus there were guest appearances from Kyle and Miss Martian. It seems that Synder's using aspects from the DCAU JL cartoon too, like that version of Hawkgirl and the Javelins.
As for the plot spoilers:end of spoilers
it seems that Starman figured out how to fix the broken Source Wall using the remaining 3 Omega Titans and something with Hawkgirl's wings but there's a chance Hawkgirl might die. There's a scene where Kendra kisses J'onn and then Brainiac attacks where it switches to Lex and his team of villains bringing Brainiac back after he died in No Justice. Brainiac and Lex take some energy from Starman because they only had 5 out of 7 or something and use it to revive some new villain(?) who the book says is the mother of the Monitor and the Anti-Monitor. WTF? Then the New Gods and the Guardians panic and ditch and you find out from Adam Strange that Apokolips and Highfather's world are gone? And they show you Lex and Brainiac with the giant woman and it ends.
Pretty enjoyable although I wish there was more action. Looks like I need to go back to the older issues and pick up future ones.