Thinking about DC universes honestly hurts my head a little.
My understanding is that all their big superheroes started out in the forties and were rebooted in the seventies. Both continuities were published simultaneously. A Flash story happened where we learned that the original superheroes lived on Earth 2, and the newish ones were on Earth 1. Both worlds fused during Crisis on Infinite Earths, but then some other stuff happened and I have no idea what’s going on.
This book reboots Earth 2, so now we’ve got old heroes in a modern setting. What happens is this: Wonderwoman, Batman and Superhero all perish defending their world from an Apokalips invasion. So a new batch of heroes need to get themselves sorted to deal with the next big essential threat. There’s a Flash noticeably styled after Hermes, a gay Green Lantern with nature-based powers, and military experiment versions of The Atom and Hawkgirl.
Earth 2 really didn’t do it for me. Maybe it’s because I’ve seen a similar premise work better in JLA: The Nail, or because the reboot didn’t sit right with me. Read something else.