What is ironic about huck's decision to go back and allow the widow to civilize him?

"Tom's most well now, and got his bullet around his neck on a watch-guard for a watch, and is always seeing what time it is, and 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."

Chapter 43/ Page 388

He's not going to allow her to civilize him, and he plans to leave ASAP. This is where the story ends!