It feels like the biggest thing DC's ever published. Even if it isn't, it feels that way. It's certainly not the best, or the best-selling or the longest-running, but it changed both the DC universe itself and the American comics industry. Even today, DC history will always be split into "pre-Crisis" and "Post-Crisis". It wasn't the first major comics crossover, but it was the first one that consciously built on its own decades of history to create a company-transforming epic. Heroes died, including famous ones. Universes were destroyed. It's huge and it knows it's huge.
This series created an industry trend for similar event crossovers, but none of them are well-remembered as Crisis still is. It wasn't just another annual stunt event. It was genuinely transformational and DC weren't doing it as a cash cow. (They weren't sure if it would succeed and only did limited marketing.) They did it because over the decades they'd built up a multiverse snarl of Earth-One, Earth-Two, Earth-A, Earth-B, Earth-S, Earth-X, etc. that was newbie-unfriendly and made their output less unified and worse-selling than Marvel's. People called them old-fashioned.
Crisis destroyed that with anti-matter. It crushed DC down to one continuity and one Earth... and, en route, killed hundreds of heroes. (That was usually offscreen as their universes got wiped, admittedly, but not always.)
That said, though, what's it actually like?
Good grief, it's big. It took me ages to read it. It's dense, it's enormous and it's deliberately showcasing the full mad range of DC's characters. Gorilla City, Atlantis, cavemen in the Stone Age, Wild West, war comics (e.g. Sergeant Rock), Swamp Thing, John Constantine, King Arthur and the Round Table, the Luthor-Brainiac team, multiple versions of Superman, the 30th century, Hawkman, Uncle Sam (and yes, it's exactly who you're imagining), Darkseid, Blue Beetle, the Doom Patrol, the Spectre, Etrigan the Demon and... look, it's everyone. EVERYONE. We see any DC planet you can think of and pretty much every century in which they set comics stories. There's Kamandi, the last boy on Earth. There's a Japanese hero called Katana, which made me wince until I remembered that these are comic book superheroes and so everyone has a stupid name.
It's a story of two halves. The first half doesn't really have a plot and just wants you to go "wow". This is successful. The sheer weight and weirdness of fictional history is pretty staggering... as they all die. Universes get eaten. A guy called the Monitor is trying to save the universe and, interestingly, he's not restricting himself to heroes. Villains are recruited too, albeit not with the fireworks you'd get from Suicide Squad. Firestorm and Killer Frost made me laugh. "Hey quit nibbling my ear."
In the second half, a supervillain emerges. He eats universes, so he can't be stopped just by punching him (although our heroes will give it a go). This is liable to be big rather than good, but the story's willingness to kill heroes makes it shocking. Two deaths in particular stand out (in an era before killing major heroes for sales purposes became something of a fad). Supergirl's is stirring and heroic in all the best ways, while the Flash's is... holy shit.
Wolfman is perhaps overly fond of making heroes say some variant of "I'm scared, truly scared, for the first time ever". I soon reached the point of "yeah, we get it". That said, though, I understand the need to underline that this maxi-series really, really wasn't just super-business as usual.
Reading this book is a bit exhausting. It's a monster. It's amazing. I'm not normally a fan of parallel universe and reality-rewriting stories, but this one's different because all that accumulated DC history means that those universes are all real. (Oh, and apparently one panel here shows the Marvel Universe being destroyed with all the others.) At its best, it's jaw-dropping... but I wouldn't want all stories to be like this. I have absolutely no interest in reading all the event crossovers that it inspired, many of which tried to sort out and/or reboot the continuity holes and niggles that were created by Crisis itself. These include Zero Hour: Crisis in Time! (1994), Infinite Crisis (2006), 52 (2007), Final Crisis (2008), Blackest Night (2009), etc. Retcons for the sake of retcons are one of my least favourite things in comics.
That's not Crisis, though. Crisis is special.