Help with a quote in Huckleberry Finn?

Twain was also consciously writing against Romanticism in novels, such as exemplified by Walter Scott and Alexandr Dumas. He parodied the conventions of the Romantic novel (look at Twain's 'royal' characters compared to Scott's; consider the hilarious scene where in order to rescue Jim he first has to sneak into the place from which he is to be freed.) So, I think his admonition at the beginning was Twain's way of pointing to the past, telling critics to look at the work in another light, and to tell his readers, in effect, there's a hell of a yarn in this book which you can enjoy without resorting to critical sophistry. I do agree with the earlier response that there is sarcasm in Twain's message here.