I found the book fairly unbiased. People who approach constitutional law with an idea that it's supposed to be some thing or other may find some of the facts disturbing, but the authors really do seem genuinely focused on their project of trying to determine whether the decisions of the Supreme Court relate to Public Opinion in any way (e.g., being influenced by it, or influencing it). So they look at whether pressure builds or fades after big court decisions.
Now, I'm only a little bit interested in that project . . . but I'm fairly interested in what the public opinion around all these topics has been, is, and is becoming. And so I usually found the presentation of that clear and well-organized. Sometimes the statistics went a bit over my head, but the authors do a good job of explaining in lay terms what's been done (e.g., "we controlled for other variables" instead of "multivariate regression analysis," or some such thing). So a statistician may be able to dispute the claims being made around any given set of data (and presumably each side of most of these debates has employed statisticians to make the facts look best presentable in the past).
I found it a helpful orientation, with some things that surprised me. I haven't read each chapter, but the four or five that were of personal interest were well done and certainly sufficient to get the flavor of the book. Four stars, with one held in reserve because the author's actual topic may be a bit too arcane for most readers to find compelling.