President Richard Nixon’s decision to install a secret recording system — and then to retain the tapes — perhaps ranks as the most consequential self-inflicted political wound of 20th-century America. The criminality, abuse of power, obsession with real and perceived enemies, rage, self-focus, and small-mindedness revealed on those tapes left him abandoned by his own party and forced him to resign 40 years ago.

To date, the dissemination of some 250 White House conversations has defined his presidency and its corruption. Now comes John W. Dean, Nixon’s White House counsel and later his chief accuser, to transcribe and analyze at least 600 new conversations in his book “The Nixon Defense.” The title is misleading, because it suggests there is a case for Nixon’s innocence. Dean quickly clears that up when he writes in the preface, “Fortunately for everyone, his defense failed.”

The new material reveals further examples of the administration’s contempt for the law. It provides a detailed narrative of precisely what happened inside the Nixon White House beginning three days after the June 17, 1972, burglary when five men were arrested in the Democratic National Committee headquarters at the Watergate, and continuing until the taping system was shut down after aide Alexander Butterfield revealed it 13 months later...