It should be noted that Moby Dick is (in)famous for its very large and unusual vocabulary. Some lighter reading might yield better results for demonstration purposes. Also, while fairly long for a single novel, the number of words is still minuscule compared to what other LMs are trained on. Using the entire Gutenberg library, or a Wikipedia dump, could improve the quality dramatically.

Of course, it doesn't really matter, as the whole thing is obviously just a toy, but I still think that this approach should be able to produce much better output than the garbled Moby Dick example.