Other things I enjoyed:
The author’s ability to characterize briefly and pungently–Dr. Swenson’s letter is so revealing about who she is.
The author’s ability to create open questions that draw us along: “Karen Eckman sat in a two-story brick colonial thinking her husband would be coming home as soon as he could make Dr. Swenson listen to reason.” !!! Now I want to know what’s going on.
The author typically uses present tense for flashbacks while the forward action of the story is told in immediate past tense. I think this may be the first time I’ve encountered such an approach and I really liked it, as it helps address an issue with flashbacks (that they remove any sense of immediacy from the story).