So i just finished the blackets night run and i read the storyline version (basically blackest nighz mixed with the side stories if you dont know what i mean). Brightest day has 140 issues if you count the side storys to the main story line. And how should i read it? The core storyline (just brightest day) or the full story (brightes day with the story lines mixed)?
You can read the full Brightest Day series itself (#'s 0-24) without the side material.
The main book is the crux of the whole thing. Everything else expands upon the main beats of Brightest Day and isn’t 100% necessary to a full enjoyment of the series. It is fun of course, but not mandatory.
I’d say the closest to really connecting to the main story is the GL/GLC arcs. Outside of that, it’s more how those characters react to the news status quo, not really affecting it.