I found this section of the Bolton book -- and a remark made by then-WH chief of staff John Kelly -- rather jarring.

Bolton writes of Trump's "vindictiveness, as evidenced by the constant eruptions against John McCain, even after McCain died and could do Trump no more harm...

2/ "Another example of his vindictiveness was Trump's August 15 decision to revoke former CIA Director John Brennan's security clearance."

Bolton didn't like Brennan but didn't approve of the move, either...

3/ Kelly tells Bolton that he and the president argued about the move.

"Kelly told Trump it was 'not presidential,' which was true, and he told me it was 'Nixonian,' also true. 'Has there ever been a presidency like this?' Kelly asked me, and I assured him there had not..."

4/ "In what by this point was already an emotional discussion for both of us, Kelly showed me a picture of his son, killed in Afghanistan in 2010. Trump had referred to him earlier that day, saying to Kelly, 'you suffered the worst.' ...

5/ "...Since Trump was disparaging the wars in Afghanistan and Iraq at the time, he had seemingly implied that Kelly's son had died needlessly. 'Trump doesn't care what happens to these guys,' Kelly said. 'He says it would be "cool" to invade Venezuela.'"...

This is the former national security adviser, quoting the former WH chief of staff -- a retired Marine General who lost a son in Afghanistan -- saying that the president doesn't care what happens to U.S. servicemembers.