When it comes to Authorship Attribution do give the following topics a read.
Authorship Attribution
Increasing the sample size
The Enron application we used ended up using just a portion of the overall dataset. There is lots more data available in this dataset. Increasing the number of authors will likely lead to a drop in accuracy, but it is possible to boost the accuracy further than was achieved here, using similar methods. Using a Grid Search, try different values for n-grams and different parameters for support vector machines, in order to get better performance on a larger number of authors.
Blogs dataset
The...