Can't remember the name of a book

ok this is driving me insane! i read a book about 3 or 4 years ago and i Can't remember the name of it. its an adult fiction book i believe and it was about a family the main character was a teenage girl maybe a boy i don't remember and there is a newscast that there is about to be a nuclear war so the dad takes his family underground into this war protected thing way under the ground and hes the only one that has contact with the outside. then toward the end of the book the mom starts going crazy and the kids find out that the war nuking or whatever never actually happened so after a decade or so the kids try to get out but the dad absolutely refuses. i think i got that right but i cant remember the name of the book.

Sounds remarkably like the plot for the Fallout 3 video game. :-)