Total first-week ebook sales for Steig Larsson’s instant bestseller The Girl Who Kicked the Hornet’s Nest amounted to nearly 30% of all units sold, according to a report today from Publisher’s Marketplace.

The popular subscription-based book industry website’s mid-day newsletter is reporting that “Knopf Doubleday spokesman Paul Bogaards says their internal figures show an approximate first week sell-through of 425,000 units–which includes 125,000 ebook editions.”

If we do the math for ourselves, this translates into a 29.4 percent ebook share of the title’s total sell-through, which would be by far the largest percentage yet reported for ebook sales of a major trade bestseller.

By comparison, published reports of the total ebook sell-through for Dan Brown’s The Lost Symbol last year put it at less than 10 percent of the title’s overall sales, despite the fact that ebook sales outperformed hardcover sales on the Amazon.com website for several weeks.

At that time, many observers believed that the Kindle Store accounted for 85 percent or more of the ebook content market. Although it is widely assumed that Apple’s launch of the iPad and the iBooks store would cut into Kindle content market share, none of Larsson’s bestselling books are available from the iBooks Store due to the decision by Random House to stay clear of Apple’s agency price-fixing model.

Instead, it appears that, at least in this case, Amazon and Barnes & Noble may be the biggest bookselling beneficiaries of the phenomenal popularity of the iPad, which sold 2 million units in its first 59 days. Both Amazon and B&N; have popular ebook platforms for the iPad, and unlike Apple, they actually stock Larsson’s books.

Publishing industry observers have been fond of saying that print books still account for over 90 percent of all book sales, and that any tipping point for ebook sales is still a long way off.

We will not be hearing such pronouncements much longer.