The social concerns of Defending Billy Ryan are familiar ones for readers of Higgins's fiction: Ambitious prosecutors pursue a case against Billy Ryan, the good-old-boy Commissioner of Public Works for the Commonwealth of Massachusetts. The realpolitik of the American legal system, good-old-boy networks, political peculations, Massachusetts, and Irish-American families — these are Higgins's perennial concerns. He handles them here with accustomed ease and expertise.

The central theme of Defending Billy Ryan, again as in most of Higgins's fiction, is power. He is fascinated by the ways men (and sometimes women) jostle and maneuver for advantage in their relations with other people. The struggle may occur in the local competition of politics or the formal arena of the courtroom, or in the intimate spaces of a marriage or even a conversation. But Higgins's characters seem always in pursuit of some step up on their fellows. Because Jerry Kennedy inevitably owns his narrative, it is his pursuit of advantages that preoccupies the novel. He employs a variety of conversational tactics to hold the initiative against the prosecutors, a key prosecution witness, character witnesses, his own client, his own client's family. These tactics and what they reveal about the motives and manners of contemporary Americans comprise the fascinating core of the novel.