This is another solid effort from Elizabeth Wein, but it fails to live up to the high standard she set with Code Name Verity. 
 Unlike her last two books, this one never has a sense of urgency, even though you know from page one that the main characters are in peril. I think part of the problem is Wein's continued reliance on a narrative structure consisting of journal entries and letters. This puts the action at a remove and takes away some of the tension from the very serious situations her characters have found themselves in. And unfortunately, these documents are written by both main characters, and I had a very hard time remembering from journal entry to journal entry who the writer was until the other character was mentioned by name; their voices were just not very distinguishable from each other. 
 There's also a heavy reliance on coincidence that makes plot points both predictable and contrived. 
 I'm still a fan, but I hope Wein tries a different style with her next book.