The reason for this is that apparently some teachers and schools won’t teach the novel because of the controversial and difficult nature of discussing this word with students. So, this edition is proposed as an alternative to not teaching the book at all.
To an extent, this is sound logic. After all, exposing people to the story (minus a few details) is better than if they couldn’t read the thing at all. On the other hand, is anyone really capable of preventing people from reading Huckleberry Finn (or any out-of-copyright work) these days? It’s on Wikisource.
Besides, students are notoriously bad at following what teachers tell them. Therefore, I would guess that the best way to get students to read the book is to expressly forbid them from reading it, or at least emphasize its taboo content.
In my experience, the people who want to read and understand literature will go and do so on their own. Those who do not, meanwhile, will not learn even if forced to. I’d say the easiest thing is to write down the name of the book and the author and then tell everyone they shouldn’t read it because it is offensive. This way, only people who don’t mind the risk of being offended will bother to read it. Those who do mind can read some inoffensive book.
Then, when test time comes, the teacher can offer the students a choice of which book to write about.