About once a month over the course of his presidency Bill Clinton would unburden himself to Pulitzer Prize-winning historian Taylor Branch. Last year, Branch published the taped revelations, heavily edited and embellished with his own commentary, in an overpraised but useful volume called “The Clinton Tapes.” I say “overpraised” because anyone who knows the underside of the Clinton White House can see how Branch allowed, even encouraged, Clinton to spin a selectively remembered, self-absolving account of his presidency. I say “useful” because every now and then Branch caught up with Clinton before the White House has had a chance to...