"Shannon's Way" is not billed as a sequel to Dr. Cronin's last novel, "The Green Years." It may be read as an entity in itself, and judged on its own doubtful merits. As a sequel, it seems a pale coda to the first volume—or, should we say, a tenuous suspension-bridge to other episodes in Robie's glum saga? As a self-sufficient account of a young Scotch doctor's struggle to make a name for himself as a researcher, his lonely ragings as he trods his chosen path, and the standard females who console him en route, it is a sketchy scenario indeed—something that Dr. Cronin might have jotted down on odd bits of paper with a blunt pencil, and never endowed with a third dimension….

Since Dr. Cronin never takes the time to dramatize [Robie's individual pursuit to isolate an influenza bacilli] properly, or even to explain the...