England is so awesome and idyllic for the upper classes it's better to be there in wartime than say, NYC without a war.
I don't argue with that. Hell, it's why I watch Downton Abbey or Brideshead Revisted.
It's interesting to see how different people have addressed the idea of teen-aged girls in war. Pilcher's heroine was fired up, and volunteered, and got shuffled into a uniform and working as a waitress for the navy, and got herself married to the first young officer she slept with in WWII. No doubt there were more than a few who had similar experiences. Wein's heroine starts off in a similar way, but is distracted by actually having meaningful war work, rather than by romance.
Authors of books about the next world war have taken a very different turn from those precedents, although not so much from each other. These heroines are mostly committed to keeping people fed, first, and the resistance, second. Both Collins and Rosoff gives their young women even younger girls to look after. There is some romance, but it is very much not the most important thing, survival is paramount. And I like that these young women all have the smarts to learn new skills and develop new strategies.
Mostly what I had heard about Rosoff's book was romance-with-first-cousin. I don't consider that a big deal in real life, let alone fiction. I'm much more interested in the story of young women finding the courage within themselves that they never knew was there. For that, I would recommend any of these books. But Rosoff's gets special bonus points for being a hellish version of The Wind in The Willows, with idyllic country life made nightmare. And also, it has goats.
I'd particularly recommend it for a younger or less enthusiastic reader, despite the sex (which is all off-screen and non-specific). Daisy, at 15, has a younger voice than the heroines of the other books, and the book is shorter, zippier. How I Live Now would make an excellent gateway drug to other young women in war stories, and also works as a survival story for the actions junkies.