Twain can be tedious because he’s a humorist and we’ve heard those jokes a million times by now. Also he writes speech in dialect which now means nothing to us and makes him harder to read. I find him easier to read as an adult but he can still be a slog.

I think a lot of classic American lit is hard as an American kid because it’s removed enough from today that you don’t get the nuances and also so influential that the storytelling feels trite, even if it was revolutionary at the time.