Books 15-16/12: Fruits Basket, v. 11-12 by Natsuki Takaya; Los Angeles: Tokyopop, 2004-; ISBN v. 11 1595324062, v. 12 1595324070.
Not a ton to add for volumes 11 &12 – you get introduced more fully to the last two members of the Zodiac, as well as the head of the Sohma family, and the plot took an expected turn (well, I was expecting it) in v. 12. Still rooting for Kyo. And v. 13 is still checked out. :(