Front Lines is definitely my favorite Michael Grant book. Having read some of the Gone series and not being overly impressed after book one this presently surprised me. While I'm not as invested in this as I was with Code Name Verity and Rose Under Fire its definitely a World War II book to remember.
Its the time period where women are allowed to fight in the war, and most men aren't pleased about it. But that doesn't stop Rio, Frangie, or Rainy from joining. They never expected to be caught up in the front lines of the battle, seeing bloodied bodies.
This is great for characterization. Grant does a good job making a realistic view of women in WWII. There are some very uncomfortable scenes with these three young women being treated awful by their fellow soldiers -- and probably realistically so.
It is rather long and there were times when I was ready for the story to finish. I think the one thing missing for me in this book was emotion, and that's why Code Name Verity feels like a stronger story for me (it had me bawling at the end).