Vladeck makes a strong case that the U.S. Supreme Court is delegitimizing itself by issuing unsigned, unreasoned orders that issue without an opportunity for the court to read any briefing or hear any argument.
The shadow docket is the docket where emergency motions are heard, and where certiorari petitions are granted or denied. It was not always the case that the court was in complete control of its own docket. It used to have a more limited, but mandatory, jurisdiction over certain types of appeals. The Judges' Bill, pushed through by extremely influential Chief Justice Taft, changed that system to one of court discretion, including both which cases to take and which issues to address in those cases.
In the 1970s and 1980s, the use of the shadow docket increased because of the increasing use of the death penalty by the states. And these cases were often brought to the Supreme Court for a stay at the last minute, largely because a person convicted of a death penalty crime couldn't challenge the method of execution or make other final collateral appeals until an execution date was set. The decision of whether or not to stay a death penalty was necessarily an emergency, one for which the court could not convene in person.
Vladeck convincingly argues that the use of the shadow docket to provide substantive relief in other situations has dramatically increased since Ruth Bader Ginsburg decided to not give up her seat on the Supreme Court in 2016 to a younger, healthier jurist and instead decided to die in 2020. Justice Barrett was much friendlier, just as a matter of statistics, to using the shadow docket than Justice Ginsburg. The scope of the shadow docket also increased. Today, the Court sometimes uses the shadow docket to summarily issue an injunction without a record (or a decision) in the lower court. The Court sometimes vacates well-reasoned 85-page orders issued by district court judges -- without providing any reasoning at all for why the district court is wrong. And the Court has been issuing these shadow docket decisions in cases in which the resulting status quo (for the time it takes for a full decision later) is a clear violation of existing Constitutional law.
Vladeck is not a partisan. He supports all the arguments he is making with citations to the cases themselves, so you can go look them up. He is advocating for decisions that are written down and provide guidance for the future conduct of government and private actors, and for the guidance of lower courts. That does not seem too much to ask.
The book is accessible and a fast read, but also gives plenty of info that most legal practitioners would not have been taught in law school.