Mary Thompson has done a number of books- in varying degrees of success-dealing with teen agers. The Steadfast Heart (1951) came to grips with real issues and was a first rate story; Hillhaven was a somewhat disappointing romance-cum-career tale, along orthodox lines. Now comes Green Threshhold where again problems of emotion and a career must be worked out. Vermont is the setting; Ginger at 16, and her architect brother, Hal, a badly disabled veteran, have come there for Hal's mental and physical health. Ginger had wanted to become an architect too, and her disappointment is intense as she admits lack of talent. Only when she learns that her bent for mathematics offers its own solution, does she find her own balance. There are other setbacks, as money is a problem- and Hal fears that his girl is in love with another man. But finally things straighten out and they come through. True blue.