However, the average training and test set error of 9.7 and 9.9 are extremely close to the RMSE scores of Douglas (10.0), Adams (12.0), Howells (11.8), Crawford (11.9) and Saltus (11.6), especially taking into account that their data would be truly unseen.
without also having examined combined models of or with other authors, it is not clear how close James and Twain are in terms of stylistic change regarding the features examined here.