You didn't read my post a few above yours, I take it?
All the 4th week books from December got bumped to early January. The day before Wednesday December 26th (the 4th Wednesday) is Christmas Day, so no shipping on that date (and most stores wouldn't have been open on that day anyway, at least here in the U.S.). And if they had tried to get the books to ship for delivery Monday the 24th, well, that's Christmas Eve, and who knows how insane that would have been.