Green Lantern focuses on Hal Jordan, with some face time for John Stewart, while Green Lantern Corps focuses on the rest of the corps, particularly Kyle Rayner and Guy Gardner, but also some of the better known alien Lanterns, such as Kilowog, Arisia and Salaak. Mogo also has an important role in that book.
My first impression is one of exhaustion. It's nothing but non-stop fighting throughout the two books. There's no time to contemplate anything. As soon as one Black Lantern is down, another pops up. There are movements afoot to ally with other Lanterns from the color spectrum, which leads to the total elimination of some Black Lanterns, but mostly it's one punch 'em up after another, with lots of telling me what's happening by various characters, because, to be honest, a lot of the time it's too hard to figure out in the art. There's just entirely too much going on.
Of course, there's bouncing around between the three titles. An honest promotion of the the Blackest Night saga would have said that all three are necessary to understand what's happening, because there's no way you could have just read Blackest Night, a realization that hit me about 3 issues into it. That's when I picked up the Green Lantern and Green Lantern Corps issues that were tied in.
My benchmarks for mega events in the big two, and particularly in DC, are Crisis on Infinite Earths and 52. Those were large events that earned the sobriquets epic and saga. I've used both terms so far with Blackest Night, but that's only in the most pedestrian sense of length of story and density of plot. In the benchmark tales there were major events with lasting repurcussions. Crisis, in particular, carried forward for many years.
What made both of those work for me, though, was that I could jump in without much knowledge of the large DCU cast of characters and enjoy the story, learning what I needed in the context. Oh, there were many characters from many worlds eliminated in Crisis with little explanation, but I didn't need to have all that to understand the significance of their loss in the context of the story. Similarly, in 52 the C list characters who became the leads in the story were well developed and I could glean what was needed to enjoy the story and follow it through.
Blackest Night doesn't do that. Even reading all 3 core titles, I don't know what was going on with a lot of it. The overall arc of fighting Nekron makes sense enough, but all the various dead who fight the heroes are bringing baggage of their own in each encounter. Sometimes there's pontificating or a flashback to explain the significance of the character. Sometimes not. Some of the Black Lanterns show up to fight and there are conversations with the heroes showing that they know each other but I sure don't.
A major factor in that is the depiction of the Black Lanterns. The decision to make all of them shaped like their living counterparts but clad in a black uniform with the Black Lantern logo, pallid or grey skin, curled back lips to expose teeth, and so forth makes them easily identifiable as dead but doesn't help much in identifying them individually. I think the black costume with the logo was a particular mistake. If the dead looked dead in physique but retained their original costumes it would have gone a long way in helping identify the character. It might have alleviated some of the exposition that was used, too.
Of course, the fact that most of the dead were minor characters to begin didn't help matters, either.
My overall view of Blackest Night and its ancillary titles is that it was better than Legends or Secret Wars II, but nowhere near Crisis or 52. Probably not as good as the Sinestro Corps War, for that matter. It's likely put an end to my cross-over reading for quite awhile, too. I like Geoff Johns as a writer, more often than not, but no matter who's writing these things now, I'm going to pass. There's always the trade if it turns out to have been any good.