For the most part, James Comey’s new book, A Higher Loyalty, is pretty much what you’d expect: the story of his personal life, his career as a government prosecutor and head of the FBI, and his tempestuous relationship with U.S. president Donald Trump.

While there are plenty of interesting supporting characters—from Barack Obama to George W. Bush to Gambino underboss Sammy “The Bull” Gravano—the prose can be dry and, at times, verge on the self-righteous. With a deeply held view on the idea of right and wrong, Comey is not shy about voicing his opinions, nor his grievances.

Of course, the big themes in the book revolve around Comey’s titanic struggle with Trump, and the the idea of a potential presidential obstruction of justice. At this point, the debate is still locked in a he said/he said standoff. As the investigation continues, will a proverbial smoking gun be found? Only time will tell.

The most exciting revelation in the book, however, is about neither Comey nor Trump, but Robert Mueller, the special counsel investigating alleged Russian vote tampering in the 2016 U.S. federal election.

A former marine and Vietnam combat veteran, Mueller is a frequently described in the press as independent, taciturn, and driven. As Comey notes, “his severe demeanor intimidates most people.”

Continuing on about Mueller, Comey writes that “word at the bureau was that he had knee surgery not long after 9/11 and declined anesthesia in favor of biting on a leather belt.”

Now that’s shocking!