The basic "city under a dome" concept has certainly been over-used well past the point of being a fresh, intriguing, plot device that draws in readers due to its novelty. If your friend can add some unique plot twists and circumstances to the basic "dome" concept - along with convincing character development - then the book can still work well without being excessively cliche.
I cant really gove you an answer,but what I can give you is a way to a solution, that is you have to find the anglde that you relate to or peaks your interest. A good paper is one that people get drawn into because it reaches them ln some way.As for me WW11 to me, I think of the holocaust and the effect it had on the survivors, their families and those who stood by and did nothing until it was too late.