Madan no Ou to Vanadis (魔弾の王と戦姫) is a light novel written by Tsukasa Kawaguchi (川口士) and illustrated by Yoshi☆o (よし☆ヲ), published by MF Bunko J. The series currently has 5 volumes.
A manga adaptation began in 2011, illustrated by Yanai Nobuhiko (柳井伸彦), published by Media Factory on Comic Flapper.
This is a gathering place for fans of "Madan no Ou" to discuss the manga, the light novel and spoilers/summaries galore!
A teaser translation project with the first chapter available has been started on Baka-Tsuki which can be found here: