From the announcement:
Unique in its sheer size and breadth, a new open dataset released by the HathiTrust Research Center (HTRC) will provide researchers with access to otherwise restricted information. The HTRC Extracted Features (EF) Dataset reports quantitative counts of words, lines, parts of speech, and other details extracted from each page of the more than thirteen million volumes found in the HathiTrust Digital Library.
Read full announcement here.