"By becoming, in effect, an author, Jim writes himself a new destiny." (Smith 364)
Jim is an underestimated character in the book. This comes from the era, I feel. Southern slaves were not, as we have learned, treated all that bad. They were, in essence, part of the white family. The children of masters and slaves all played together, among other activities. So racism did not play a major role.
I have to admit, when the term "nigger" is used I automatically think of the era that AHF is placed. That eases the term a bit as that is what black Americans were referred to then. I did not match the term to racism automatically. There are instances of it throughout the book though.
Jim had a huge impact on the novel. If it were not for Jim, there would not have been Huck. And if the story only contained Huck, it would have been really boring. Jim was the adhesive between Huck and the adventure. Clemens even went as far as to add a family for Jim. That gave Jim a lead role in the book. Although Jim was a slave who was imprisoned, he still had a voice in the novel. There are several chapters where Jim plays a major role. So in fact, he does write a new destiny.
The ending is one that probably shocked many readers. The whole town wants to hang Jim, but the doctor basically says, hey! this man helped me when I thought Tom was going to die. The town then gains a new outlook on him. Jim becomes free at the end. The whole time he was free but didn't know it. Jim's destiny has finally been reached.