I started out my "Otaku life" with anime. People called it "Japanamation" then lol. It took me quite a while to figure out that artists in japan drew comics, and then people animated those comics. Once it clicked that Id be months ahead of all my favorite anime if I started reading manga, I dove right in. The very first one I read was Inuyasha, in middle-school. A girl that sat in front of me would let me borrow them. Berserk, though, was the first manga I bought with my own money. (huge contrast there huh)
Some one else probably answered this already, but yeah, there is a Darker than Black manga. Come to think of it, I've never seen it in a book store either... I'm sure you can find the scans online though.