There are currently 2 volumes of manga released by MediaWorks, The series has also been licensed by Viz Media in 2006, however release date for the english version have not been announced.

The Artist for the manga is Sasakura Ayato, the manga was a huge sucess like the animated series and the novels, selling over 500,000 copies.

Volume 1:

Scanlation can be found >> Here <<

(Thanks to EP)

Volume 2:

Grimoire version (LE):