Just added a tag for "Our Worlds at War," which does contain some posts only tangentially related to DC's 2001 crossover, since I haven't read anywhere near to the whole thing. Sadly, if it is remembered for anything, it's unfortunate timing, with the concluding chapters featuring scenes of terrible devastation and coming out right around 9/11/2001. It's also known for killing off a mess of characters that would return in relatively short order: Joe Kelly would get a JLA storyline out of bringing back Aquaman; but several allegedly dead characters like Guy Gardner or the Kents just returned with little acknowledgement of their "deaths."
Still, I picked up a couple back issues of OWaW, and do they hold up? Um...well; we'll start with Batman: Our Worlds at War #1, "Hidden Agenda" Written by Ed Brubaker, art by Stefano Gaudiano.
Bluntly? It's like, if the X-Files and Independence Day were set in the same universe, yet Mulder still couldn't prove the alien conspiracy. Seriously, I know some writers and fans have problems going too sci-fi with Batman, for fear of the stories going straight-up 1950's-style nonsense; but it's playing too coy. Just like JLApe or Day of Judgment, this is a Batman crossover that barely crosses over, sticking closer to the Batman end of things. If you're looking for Batman vs. alien invasion, keep walking.
The first four pages of the book are two construction workers commuting to their job site, and arguing who's the better billionaire, Bruce Wayne, or President Lex Luthor. (And with those three words, this book is dated as hell for some of you...) Actually, the fourth page doesn't really count, since it's the workers getting blown up when they get to work. Later, then-Commissioner Akins gives the case file to Batman, since the Feds made the GCPD back off.
Shortly after starting the case, Batman discovers the Feds are trying to cover up a crashed spaceship in downtown Gotham. Which rrrrreally strikes me as something Batman would'a noticed: in 2001, this was Batman at his über-competent best; before mindwipe nonsense in Identity Crisis or building Brother Eye or whatever. I honestly think, the way Bats was written then, a crashing spaceship would've set off the seismographs in the Batcave or something, and Bats would've been there quicker than a pizza delivery. (This was post-No Man's Land, there's no way Batman wouldn't have seismographs!)
I'm not even sure why Luthor is bothering to cover up the aliens, for that matter: it's traditional, sure; but the general populace of the DC Universe had to be pretty aware of aliens. It may be in the hopes of salvaging something useful from the crashes, but figure Luthor probably could make more political hay from hyping up the "alien menace" that may or may not exist...
Moving on: Batman maintains he could jump into the Feds' investigation without them even seeing him, but that Luthor would know...somehow. That's not super-clear, but Bats decides to go to a Luthor reception to get some info. Bruce and Lucius Fox chat before Luthor's speech, and while they agree Luthor's a tool, Lucius wonders if it's a good idea to make an enemy out of him. For his part, Luthor makes a fear mongering speech about terror that I'm legitimately surprised predates 9/11; that also serves as a barely-veiled threat towards Bruce and Lucius. After the speech, Bruce roofies an attending NASA scientist, to pump him for information about the crash. (With a magic drug that the scientist won't remember later.)
Breaking into the crash site, Batman eavesdrops on Luthor and his men removing an alien corpse from the crash--the third such alien crash in as many weeks; all of them seemingly fleeing in blind terror from something. Luthor also mentions "the Metropolis project," which I thought was going to be Cadmus. Batman then knocks out one of Luthor's generals in his home, to steal more info, to give to Oracle, who surprisingly can't get much. Heading to Metropolis, Batman sees Talia, who was at the time working for Luthor; she sees him as well and leaves an ID card for him. In disguise, Batman finds surveillance on the short-term Superman supporting character Strange Visitor, as well as meta-human experiments, and notes for something called the Doomsday Contingency.
The next day, Batman confronts Luthor at the White House: while Batman knows everything, his proof is dicey at best, and Luthor's already had the general killed and framed as a scapegoat. Finally, Bruce Wayne visits his newspaper, the Daily Planet, to give some information to Clark Kent...
I didn't like this one as much as I thought I was going to, but it's not unreadable. It is a snapshot of some old DC continuity that was really of its time, though.