Surely there are other good books out there, but I found G. Gordon Liddy's autobiography Will illuminating, it is a pretty frank exploration of the mind of one of the major players in the scandal.

Bob Woodward and Carl Bernstein were two investigative reporters for The Washington Post, who broke the story on Watergate. Woodward wrote a book on the subject, All the President's Men (1974), which was made into a dramatic film by the same name.