It would not be far off to say that Geoff Johns basically *is* DC Comics today; of current writers, not even Brian Michael Bendis at Marvel Comics rivals him in terms of sheer personal influence and control over the wider universe. Johns' reign as DC's chief creative force arguably began in earnest with his run on "Green Lantern", which began with "Green Lantern: Rebirth", the return of Hal Jordan as the main Green Lantern (neither the first time nor the last time that Johns would retool a status quo to its Silver/Bronze Age incarnation, albeit with extra violence). "Blackest Night", an eight-issue miniseries published in 2009, represents a climax to several years of Johns Green Lantern stories, while also setting the stage for a passel of new developments in the DCU. At the same time, one cannot help but think it somewhat uninspired when compared against Johns' own "Sinestro Corps War" story, and I think DC has erred somewhat in how they've chosen to package this story. Spoilers follow.
To briefly summarize the plot, the DCU is going to hell, with two major galactic crises, the War of Light and the Blackest Night, being initiatived simultaneously. On the former case, the seven colour Lantern Corps are going to war. This development may arguably be Johns' signature addition to the mythos: he took a single Green Lantern Corps, inducted the preexisting Star Sapphires into the same schema, and created another five to fill out the spectrum, all tied to emotions (and willpower, which, as many have noted, is not an emotion). While the Lantern Corps fight each other (this development, it must be said, feels a bit rushed compared to the years of buildup), the Black Lantern Corps, who are basically zombies, begin to rise, under orders from their mysterious leader (unless you're familiar with 1980s Green Lantern comics, who it is won't mean much to you, mind) in order to purge all life from the universe and undo creation. So, a busy time for DC's heroes (and, indeed, Johns draws in a much wider cast than usual, mostly handling them well - though, in one of those annoying little details, he acts like "Diana Prince" is Wonder Woman's real name, which would be like Bruce Wayne being addressed as "Matches Malone").
It's overall a pretty good superhero story, with tremendous art by Ivan Reis (a long-time Green Lantern artist doing his last work on the property before departing for other waters within the DCU). Reis juggles an enormous variety of characters and locales, and makes them all work. However, for a variety of reasons, it doesn't strike me as being in the same league as "Sinestro Corps". Johns is an example of a pure superhero writer in a way that many/most of the other major writers in the genre today aren't, analogous to Roy Thomas or Roger Stern; Ed Brubaker, for instance, is writing books that are a hybrid of crime/noir genres and superheroes (as does Brian Michael Bendis), while Grant Morrison mixes so many influences it's hard to name them. Johns, by contrast, is basically just writing superheroes, drawing on references more or less exclusively from past comics history (he's a big fan of what is occasionally derided as "continuity porn"). At his weakest as a plotter, and somewhat in evidence here, he adheres very tightly and with little interesting deviation to a basic story template: the villains launch their big attack, they score some major hits, the heroes regroup and develop a plan, the plan doesn't quite work and the villains pull their big trump card, putting them closer to victory than ever before, then the heroes pull it out of the fire. That's pretty much what you get here.
On a final note, "Blackest Night"'s miniseries title ran concurrently with Johns-written stories in the main "Green Lantern" title that weaved in and out of the main storyline. While he tried for the most part to keep the two storylines contained, they really work best when read one after the other. DC acknowledged this when they collected the "Sinestro Corps War" story in two volumes, cutting back and forth between "Green Lantern" and "Green Lantern Corps"; that format would have been ideal here, but instead they have grouped the "Blackest Night" and "Green Lantern" issues into two separate hardcovers. It can be read that way, but I don't think it's the best way to go about it.
Recommended.