Do you know off the top of your head why this comic is important? (Relatively speaking, that is?) Chances are that if you do you've probably wasted as much of your life as I have. But we can cry about this later.
For now, we must discuss the Second Coming of one of the most distinctive aspects of 90s DC Comics - the triangle numbers. It's amazing to think there may be a whole generation of readers for whom the idea of the triangle number is a new, fresh development intended strictly to facilitate ease-of-reading across a sometimes-confusing assortment of closely related titles. The . . . well, enthusiasm would probably be too strong a word . . . let us say, the interest with which this development has been met by assorted nerddom is somewhat surprising. (I have seen more than one positive comment!) Because, for those with long memories, the idea of returning to triangle boxes means returning to some of the darkest times in the history of mainstream comics.
Yes, let's look back at the mid-to-late 90s Superman family of titles. The problem with the triangle number, as much as it was meant to simplify the reading experience, is that it was symptomatic of a creative process that ultimately ended up producing some of the blandest, most forgettable, least interesting comics that the world had ever seen. You could not call late 90s Superman bad by any stretch of the imagination, because they were was just so boring that the titles didn't even register as sensory input at all - put an issue of any late 90s Superman title down on the table and you'd have a hard time telling it from the tablecloth. Remember Conduit? Remember the Trial of Superman? Electric Blue Superman? Freakin' Dominus?
Now, of course, you can't blame these faults on the triangle, as I said above it was a symptom of a larger problem. But the problem was real: since the very beginning of the 1986 Man of Steel relaunch, the Superman books prided themselves on an extremely tight continuity, unusual at the time and still unusual to this day. Remember back in the day when it seemed like Batman and Detective sometimes occupied different planets? (Hell, those days are still with us now.) Or, better yet, let's look at Spider-Man - there was a period during the 90s when he had four different ongoing titles - and the quarterly Unlimited - and each title was so different in tone and execution that the direct comparison could be jarring. But it seemed to work pretty well for a time. Obviously, Amazing was the flagship, with the marquee superhero action; Spectacular was home to slightly darker, more street-level stories that emphasized (at least under JM DeMatteis) a more psychologically grounded milieu; and Web of Spider-Man dealt more with Spider-Man's extended supporting cast and many of the long-running soap-opera storylines that the other two titles had eased away from. (Spider-Man at the time was something of a lost child. It honestly should have been canceled after Todd McFarlane left the company, because the attempt to turn it into a Legends of the Dark Knight-ish rotating spotlight title resulted in a pile of extremely forgettable comics.) The point is that other lines tried to create a sense of variety, with different "flavors" being offered up in different titles: if you liked action, Amazing was the title for you; if you liked more focus on Peter and Mary Jane's marriage and their relationship to people like Aunt May and Harry Osborne, Spectacular was your joint.
But the end result of the Superman titles' close relationship was that they began to blend together. Rather than let each individual creative team tell the types of stories they preferred to tell, more often than not the whole line was preoccupied with large-scale macro-stories that, more often than not, did little credit to those individual creators who comprised the very large Superman team. It was, essentially, a weekly title for the duration of the 90s. Long before 52, they succeeded in making sure there was a Superman book on the stands every week for approximately ten years. Furthermore, they were so concerned with keeping the ongoing continuity intact that they even created a quarterly title, Superman: Man of Tomorrow, for the express purpose of putting a Superman book on the stands during the quarterly skip weeks that resulted from the monthly schedule. (Do the math: 12 issues a year x 4 titles = 48 issues, not 52.) That seems positively perverse now, but really, it happened, and the major selling point - the only discernable selling point - of the series was precisely that it filled a Superman-shaped hole in the quarterly schedule.
To a large part, the titles were also victims of their own success, namely, the success of the Death of Superman. I seem to recall that before the Death, the individual titles had still maintained some resemblance of individual identities, but for the duration of the subsequent year-long Death and resurrection sequence, the books were for all intents and purposes a weekly narrative, and they never really stopped that kind of tight coordination from there on out. And the success of the Death meant that for the next half-decade or so they kept trying to recapture the incredible popularity of that storyline with a series of similarly-themed Earth-shattering "events", each one a case of gradually diminishing returns. They were often titled using the repetitive formula, "The ____ of / for _____", i.e., "The Death of Clark Kent", "The Trial of Superman", "The Battle for Metropolis". (To be fair, there was also "Dead Again"). But, you can only kill the guy once, and these subsequent storylines got progressively worse.