May 25th, the long awaited continuation of Suzumiya Haruhi light novels, titled The Surprise of Suzumiya Haruhi, was released. During the first week after the release, the volume has sold 341,184 copies and set a new record for light novels. The two-volume release was the first Suzumiya Haruhi novel in 4 long years, so the excitement of fans was to be expected. Nevertheless, the sales figure is an amazing feat. It has surpassed the previous first rank holder, volume 8 of Ore no Imouto ga Konna ni Kawaii Wake ga Nai (selling 151,194 in the first week), by more than twice of the number of sold copies. Since it was a two-volume release, the actual number of sold books is twice the number of the purchases, so almost 700,000 books have been sold in the first week.
EDIT: The previous information about counting one purchase as two sold copies seems to be false.
Source : Oricon