Bob Woodward — in an eye-opening excerpt from his forthcoming memoir, "Secrets," that's previewed in the new issue of The New Yorker — reveals that one of his best friends, the late Richard Darman, was also one of his best sources during the Ronald Reagan and George H.W. Bush administrations.

"Darman was willing, even eager at times, to talk about the most sensitive intelligence matters, including N.S.A. intercepts and covert C.I.A. operations," Woodward writes in his book , out Nov. 15. "He was always careful not to talk about matters that would harm national security, I believed, but he would go right up to the edge — a reporter's dream source."

Why it matters: Woodward, 83 — who followed the blockbuster Watergate reporting of his youth with a shelf of revelatory books about American presidents — gives a searingly honest account of the collapse of his friendship with Darman after a Post series that was damaging to Bush.…