Initial reports on Dark Knight Strikes Again indicate that the title has been selling briskly since its Wednesday, December 5 release.  Sales are being powered by a solid public relations effort by DC, with the top two articles so far probably the coverage in the December 7 Entertainment Weekly (which also previewed the first two pages of art) and in the December 5 USA Today (which flagged the articles on its cover and placed an article on the front page of the Life section, and an interview on 7D of the Life Section).  Other coverage has appeared in the New York Daily News, Chicago Sun Times, Seattle Times, Salt Lake City Desert News, as well as an interview and story prominently featured in The Onion. 

Reorders exceeded DC's expectations significantly enough in the UK that Diamond has exhausted its copies there and will not have more available until this Thursday.  In the U.S., Diamond has stocked copies at all of its regional warehouses, and DC opened on Saturday to have its reps available to take reorders.  Anecdotal reports from retailers here are that the book is meeting or exceeding expectations.  Of course, in addition to reorders, many retailers scheduled additional copies to arrive over the next four weeks, using DC's unique staggered shipping program to spread out their copies. 

DKSA is the first million dollar comic in at least five years (see 'Return of the Million Dollar Comic'), and seems poised to be a publishing event of similar magnitude to its predecessor fifteen years ago.  That release produced a Dark Knight trade paperback that has sold over 500,000 units, so the top end of where this title could end up is a lofty number for a $7.95 periodical.