The Question and Answer section for Life is Beautiful is a great resource to ask questions, find answers, and discuss the novel.
People and circumstances rarely go the way we want them to. Bad things happen like war. Despite the upbeat beginning, Guido begins to be harassed by the Fascists. Soon he, Eliseo, and Giosue are taken away on a train to a concentration camp.
Unfortunately I do not recall the beginning of the movie, I saw it so long ago.
Unfortunately I can only comment on the book.