Because readers have undoubtedly been counting down the days on their calendars, it's probably unnecessary to say what today is -- but we'll do so anyway: It's Sept. 25, National Comic Book Day!

No, not Free Comic Book Day; that's in May. National Comic Book Day, the unofficial holiday whose origins are as mysterious as its observers are scarce. As we noted last year, no one takes credit for its founding -- heck, no one seems to know when it began -- it receives little to no industry support, and there are no traditions tied to it (however, you can always try asking your local retailer for a free comic).

While a smattering of local grassroots events (see the photo above) have popped up in previous years at colleges, libraries and the like, this year comiXology is marking what it humorously dubs as "The Nth Annual National Comic Book Day" with a one-day offer: more than 25 digital first issues, ranging from Southern Bastards and Lumberjanes to Stumptown, Vol. 3, and Quantum and Woody, for free (just enter the code "Comics" at checkout). The deal ends tonight at 11:59 ET.

On the Scholastic blog, Archvillain author Barry Lyga observes National Comic Book Day with a brief essay about how comic books have always been misunderstood.

Elsewhere, Catster (yes, Catster) celebrates the holiday with a list of its favorite comic-book cats, while these crafters recommending creating comic book coasters ... by cutting up unwanted comics. And a search of Tumblr shows only a few fans (so far) embracing the occasion by celebrating their favorite comics and characters, and encouraging others to support their local comic stores.

How are you spending National Comic Book Day?