Doctoral dissertations are not published books, but can be considered book-length scholarly studies.
W&L subscribes to a database which offers the complete texts of over 1 million dissertations and theses.
Described as "the world's most comprehensive collection of dissertations and theses," this database contains over 2.7 million citations to dissertations and theses from around the world, dating back to 1861. About 1.2 million items are provided in full-text (PDF) form.