The main theme could be about redemption. In many such novels, characters who are in difficult or morally ambiguous situations strive to redeem themselves, like a 'dead man' in a sense of their past actions coming back to haunt them but still trying to make things right.
I'm not sure specifically as there could be many different versions of a novel with this title. But generally, there might be a protagonist who is in the situation of being a 'dead man walking', perhaps a wrongly accused man facing execution.
Michonne does die in the comics. The circumstances surrounding her death were quite dramatic and had a significant impact on the story's progression. It happened during a major conflict with other characters.