Former national security adviser H.R. McMaster wants you to know he has not written the book you probably wanted to read — and he says it right up front.

"This is not the book that most people wanted me to write ... a tell-all about my experience in the White House to confirm their opinions of Donald Trump," the author warns in his preface.

That might have been "lucrative," he says, but it would not be "useful or satisfactory for most readers."

McMaster, who served as national security adviser to President Trump from March 2017 to April 2018, has instead written a book that he hopes "might help transcend the vitriol of partisan political discourse and help readers understand better the most significant challenges to security, freedom and prosperity."