When Yukito Kishiro first created Gunnm (Battle Angel), he started with the world. It's basically future post-apocalyptic, but it's well thought out, and perfectly feasible. He even has little notes here and there throughout the book giving details on some of the new (or old) technology. Like most manga, the artwork is fairly simple, but beautiful. Vehicles, landscapes, character designs.. you name it. All of it has that futuristic dirty feel to it that the original Star Wars movies have, with more than a bit of Mad Max thrown in. But, the characters are where it's at. The main character starts at the bottom. She is literally found in a trash heap. Her character development, as well as the man who finds her, are very well done. There are a lot of internal struggles as well as external, and no punches are pulled. As she tries to figure out who she is and who she was, the world begins to expand with her travels. And, those outside influences that are only at the edge of the story in the beginning start coming into play.
There are nine original books. Then, Kishiro took a ten year hiatus. Rumor is he was sick. When he started again, he retracted the ninth book and continued with a series called Gunnm: Last Order. Off to my next stop...