President Trump Donald John TrumpUS reimposes UN sanctions on Iran amid increasing tensions Jeff Flake: Republicans 'should hold the same position' on SCOTUS vacancy as 2016 Trump supporters chant 'Fill that seat' at North Carolina rally MORE in an early morning tweet on Thursday mocked his critics and those who write books about him, pointing out that he's in the White House and "they're not!"

"So great to watch & listen to all these people who write books & talk about my presidential campaign and so many others things related to winning, and how I should be doing 'IT.' " Trump wrote on Twitter.

"As I take it all in, I then sit back, look around, & say 'gee, I’m in the White House, & they’re not!" he added.

So great to watch & listen to all these people who write books & talk about my presidential campaign and so many others things related to winning, and how I should be doing “IT.” As I take it all in, I then sit back, look around, & say “gee, I’m in the White House, & they’re not! — Donald J. Trump (@realDonaldTrump) January 31, 2019

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It was unclear what sparked Trump's tweet, but it comes shortly after former White House communications aide Cliff Sims's new tell-all book, "Team of Vipers," was published.

The memoir details Sims's time in the White House and reportedly describes dysfunction within the White House.

The Trump campaign said Tuesday that it was preparing a lawsuit against Sims for violating a nondisclosure agreement (NDA). Sims said this week that he's not concerned about a possible lawsuit.

In addition to Sims's book, Trump ally and former New Jersey Gov. Chris Christie (R) also has a new book out. Christie's memoir, "Let Me Finish," is reportedly critical of Trump's son-in-law and White House adviser Jared Kushner Jared Corey KushnerAbraham Accords: New hope for peace in Middle East Tenants in Kushner building file lawsuit alleging dangerous living conditions Trump hosts Israel, UAE, Bahrain for historic signing MORE.