In her focus on ordinary people caught in extraordinary situations — and coming out ahead — Isaacs's novels present a generally optimistic view of life. She is also a sharp observer of contemporary mores and typical problems of an era. For this reason the books hold up a provocative mirror to each of the decades that they're set in, as well as to concerns in some readers' lives.

1. Shining Through has been criticized for the implausibility of its spy drama: that a hastily trained ex-secretary could function successfully as a spy in Nazi Germany, for example. Do you find this a fair criticism? Does it make any difference to readers' enjoyment of the book? Should it?

2. The first two-thirds of Shining Through is devoted to Linda Voss's life as a legal secretary and dutiful daughter, and then to her subtly disappointing marriage. The action plot in...