Historian Douglas Brinkley of Rice University notes that it's "almost mandatory" for first families to have a pet, adding, "We demand a first pet."
"So many Americans have dogs and cats and it makes us feel like the first family is one of us," Brinkley said.
The public fascination is shown in the book, too: There's a photo of a greeting card featuring the Clintons' first cat Socks, complete with a paw print "signature," a photo of Laura Bush holding Scottish terrier Barney eyeing a chocolate replica of himself and a picture of a cookies being decorated depicting Bo, President Barack Obama's Portuguese water dog.
Anita McBride, Laura Bush's chief of staff in the White House who currently teaches at American University, was among former staffers interviewed for the book. She notes that it was Barney who "opened up the White House to the public" after the Sept. 11 terrorist attacks.
With a tiny video camera on his collar, he helped record a tour of the White House's Christmas decorations. The Barney Cam was such a hit that it continued for the rest of Bush's presidency.
"The pets really were a big part of helping to tell the story of life in the White House," she said.