My very first fanfic-writing fandom was Warhammer 40K, mostly so I could write backstories for my tabletop army. But the inviting thing about the 40K universe was that it is an amazing mixture of your lists's #1 and #2—fantastic detail and depth in some areas, complete nulls in another, and a canon that is completely self-contradictory. So you take what you like and you make it yours.

The last part—this romance stuff—is all new to me, but I'm growing into it. I like to think my stuff is character driven, and romance is a pretty good drive, right?