A dozen different titles? Wow. There must be extra comic books that I didn't pick up because all I know is the ones that I got. It started out as a typical on-going monthly comic book series but then somewhere along the line they decided to turn the issues into graphic novels. There are six graphic novels that contain every issue. I have book one through six. I don't think that the singular issues are still being printed but you may find them still in comic shops scattered around. Read Book One until you reach Book Six. They should be found in the adult section of comic book shops or in the manga section.