I love learning new bits of history, and this book has a plot hinged on a fascinating aspect of WWII homefront danger that I'd never heard of before (and won't share, for spoiler reasons).
For all that the story begins with Dorie and Gordon's brief love affair via letters, it isn't a romance--just a journey to restored friendship, which I think works better; those two would have a lot of points of contention in fundamental areas, which would make marriage a challenge. I wasn't too keen on Dorie at first--despite her convictions in supporting the war so far as to become a WAC, she practically lives to thumb her at authority when it interferes with what she wants. But her audacity is admirable at other times (and I know the value of a friend who can talk their way into or out of anything), and she grew on me. I related much more with Gordan's quieter, more introspective personality.
A major facet of the story is pacifism vs serving in the war effort. Gordan lands squarely on one side and Dorie on the other, but in the end both learn some value of the other's stance. I think the author strikes an excellent balance between the two sides. Even within the pacifist side, there are different viewpoints expressed by various characters--a non-religious communist, an extremely religious dogmatic, a black man, a jokester. It's a group of men who are united by a job and a shared moral belief, but they're still all just men with different personalities and histories that shape the way they view life.