"The Lines Between Us" by Amy Lynn Green

Since the attack on Pearl Harbor, Gordon Hooper and his buddy Jack Armitage have done “work of national importance” in the West as conscientious objectors: volunteering as smokejumpers, parachuting into and fighting raging wildfires. But the number of winter blazes they’re called to in early 1945 seems suspiciously high, and when an accident leaves Jack badly injured, Gordon realizes the facts don’t add up. A member of the Women’s Army Corps, Dorie Armitage has long been ashamed of her brother’s pacificism, but she's shocked by news of his accident. Determined to find out why he was harmed, she arrives at the national forest under the guise of conducting an army report...and finds herself forced to work with Gordon. He believes it’s wrong to lie; she’s willing to do whatever it takes so justice will be done. As they search for clues, Gordon and Dorie must wrestle with their convictions about war and peace and decide what to do with the shocking secrets they discover.

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.