Forty-eight days before the release and she’s already topped Dan Brown’s latest conspiracy-theory casserole at both top retailers. To put that in perspective, note that the book doesn’t even have a cover yet. So much for the Page Six hit piece about demand for her being slack.

No way to tell yet, obviously, whether the monster launch will have legs or whether it’ll deflate a bit next week after Palinistas are all done ordering their advance copies. But if it goes on to become a mega-seller, it’s a game-changer insofar as it’ll establish her unquestionably as the most prominent Republican in America, which leaves Huck and Mitt in an awkward spot before the primaries and presents the media with an interesting choice. Do they try to spin the sales as unrepresentative of her support among Republicans given that plenty of liberals are bound to buy the book for campaign dish and insight into the Palin “trainwreck”? Or do they follow lefty conventional wisdom that Palin would be the easiest person to beat in 2012 and talk up her appeal to Republicans to try to nudge her into a presidential run? (Righty conventional wisdom, of course, is that she’s the candidate the left most fears, but given their expectation of future Couric-type disasters during a campaign, I’m skeptical that that’s true.) Only one thing’s certain: If she hasn’t already been signed to write a second book, she will be soon. “Common Sense Conservatism” by Sarah Palin, perchance?

Update: Prognosis for mega-sales: Good.

HarperCollins will print 1.5 million copies for the book’s first run, the same number that was printed for late Sen. Ted Kennedy’s memoir “True Compass.”

Kennedy’s book, published earlier this month, currently stands at number six on the Amazon list.

A publishing industry source told POLITICO that they “cannot remember a non-fiction book taking off like this in the pre-order market. It became number one only a couple of hours after nothing more than a date announcement. It is truly unprecedented.”

Much of the 400-page book is based on journals Palin kept during her vice-presidential run.