President Donald Trump finally let loose Saturday on his niece Mary Trump for her harshly critical book about him, calling her “unstable.”

He also blasted Washington Post journalist Bob Woodward and former national security adviser John Bolton, who both spilled — or will spill — damning details about him in books.

Trump tweeted that only books that make him look bad have a chance at being published.

He called Bolton a “dumb warmonger” in an attack tweet. The worst he could call Woodward was a “social pretender” with nothing good to say.

But Trump was particularly vicious about his niece. He said she was “rightfully shunned, scorned and mocked her entire life” and was “never even liked by her own … grandfather.”

Mary Trump delivered her own stinging blows to the president in her book, “Too Much and Never Enough: How My Family Created the World’s Most Dangerous Man.”

Mary Trump also recently released secret audio recordings of Trump’s sister, former federal judge Maryanne Trump Barry, who ripped the president as a man entirely without principles, a liar, a cheat and cruel.

Barry called Eric Trump “the moron” and characterised Ivanka Trump as callous and self-absorbed as the administration separated migrant children from their parents.

Mary Trump told The Washington Post that her uncle is “unfit” to be president and that she will do “everything in my power” to make certain he doesn’t win reelection.

Woodward examined the president’s response to Covid-19 in his upcoming book, “Rage,” and obtained copies of 24 letters between Trump and his one-time pal, North Korean dictator Kim Jong Un, CNN reported earlier this month. 

Woodward reportedly conducted 17 interviews with Trump for the book, which is due September 15.

Trump on Friday tweeted that the book was “a FAKE” — even though he hadn’t read it.