D Prize Ichiban Kuji from Code Geas in Wonderland.  While its not 18+ it is a little on the ecchi side (maybe PG13), book is new and has been shown out of plastic to a few in person customers.  Full color, concept sketches and all kinds of neat art from Code Geas in Wonderland.

Code Geas in Wonderland ArtBook Ichiban Kuji D Prize