Joan Biskupic says her fourth book about a member of the United States Supreme Court involved “my most difficult subject” – Chief Justice John Roberts. But, perhaps in good part for that reason, it is also attracting much attention.

Roberts is “a very reserved individual,” Biskupic said during an “On the Issues with Mike Gousha” program in the Lubar Center at Marquette Law School on Tuesday. “There’s a lot that you see, but much more that’s held back.” She had the benefit of eight interviews, covering more than twenty hours, with Roberts, but she said she wonders still about what is not known about him.

However, Biskupic’s newly-published biography, The Chief: The Life and Turbulent Times of Chief Justice John Roberts, does offer a lot, some of it not reported previously, about Roberts, who has been chief justice since 2005.

And in addition to a richly detailed description of Roberts’ life, the book breaks new ground in describing how Roberts came to be the decisive vote in upholding the constitutionality of the Affordable Care Act, often known as Obamacare, in 2012. Biskupic describes how he initially took positions opposing the constitutionality of the law during the court’s work on the case, then switched his views.

“I think he definitely did not want the whole law to go down,” she said. “I’m fine with saying I don’t know why, for sure.”