President Trump is not a favorite in the extended Bush household. Former President George Bush considers him a “blowhard,” only interested in feeding his own ego. Former President George W. Bush, his son, thinks Mr. Trump fans public anger and came to office without any understanding of the job.

And both worry that Mr. Trump has blown up a Republican Party that they spent two lifetimes building, a party that was once committed to removing boundaries to trade and immigration, promoting democracy and civil society and asserting a robust American leadership role in the world, according to an author who has interviewed them.

A new book on the two Bushes who served in the White House provides a glance at their apprehension over Mr. Trump’s rise to power and what it means for the country. The first book ever written with their cooperation about their relationship, it also opens a window into the only father-and-son tandem to hold the presidency since John Adams and John Quincy Adams.