The ending of Mark Twain'sThe Adventures of Huckleberry Finnbasically concludes the action in a full circle, providing the reader with two very important devices: The surety that the goals and problems of the main character have been fulfilled, and an assurance of possible future adventures.
The excellent craft in narrative that Mark Twain offers, speaking as Huck, literally submerges the reader in the life of Huckleberry, actively experiencing every event while vicariously letting the reader discover, in awe, all the new things that Huckleberry learns as a growing boy.
This is more than likely the reason why Twain titles this last chapter: "Chapter The Last: Nothing More to Write". However, there are some things that occur in this chapter which particularly may satisfy the reader, depending on the reader's particular affection towards Huck. For example, it is in this chapter when Jim tells Huck that his father will never return. This is satisfying because now we know, for sure, that Huck is and will always be safe from his father's abuse. Moreover, we know that his father died the death that he may have deserved.
Doan' you 'member de house dat was float'n down de river, en dey wuz a man in dah, kivered up, en I went in en unkivered him and didn' let you come in? Well, den, you kin git yo' money when you wants it, kase dat wuz him
Second, "The Last" chapter also is satisfying because Jim is rewarded by Uncle Silas, Aunt Polly and Aunt Sally for helping the doctor nurse Tom in a very nice way, providing him with food and comforts that, as a slave, he would have never dream of. Furthermore, Tom gives him forty dollars for having accepted the "task" of acting as their kidnapping victim. That particular reward is Jim's absolute favorite, and for sure will seal the friendship between himself, Huck, and Tom.
Finally, we see that Huck himself tells us that writing a book is hard, and that he if he had known how hard it is he would have not started writing. He closes the door to the action but, like he says, he has to "light out the territory" ahead of the rest. This means that he will leave the window open to future adventures, save he becomes "civilized" by his aunt. This is a sweet way to end a wonderful tale of growth, adventure, curiosity, and wonder especially when the young man, himself, is who waves the reader "good bye" and assures us that he will be around someday again.
[...]so there ain't nothing more to write about, and I am rotten glad of it, because if I'd 'a' knowed what a trouble it was to make a book I wouldn't 'a' tackled it, and ain't a-going to no more. But I reckon I got to light out for the territory ahead of the rest, because Aunt Sally she's going to adopt me and sivilize me, and I can't stand it. I been there before.