Night is a book about a boy experiencing the Holocaust. But then why does the title seems to have no relation to the Holocaust? The simple word "Night" can mean anything, it could be a metaphor, or a "meta-more"; or a bunch of metaphors bundled into a single word. To a freshman in high school, the title seems to have many meanings, it could be the "dark" times that were happening, it could be the darkness that leads to eventual light, or it could just be a random word the author selected. For whatever reason its name was titled, the book's ideas still rings true in our minds.
Night could be a sadness word. It might be an explanation of the horrible darkness that preyed upon some people in the world at that time. Our protagonist in this story is a Jew, but many other people were prejudiced against during the time period. The "gypsies", as they were called, were ostracized by the Nazis, as well as the Jehovah's Witnesses, the Roma, the homosexuals, and the mentally and physically disabled. They were all selected out, and sent to various camps and Facilities, where they were tested upon and killed without cause. Merely because of belief or disability, people were killed. It was indeed a "dark" time for the European world.
Night could also symbolize hope; an eternal faith in the fact that after darkness and night, comes morning, a bright time away from the darkness. The title could symbolize the author trying to keep his hope during that time, or trying to survive to the eventual daybreak he knew was due. He was having a horrible time, and the thought of a "dawn" of a new tolerance for his beliefs probably kept him going.
On the other, more literal hand, it's always possible that the author just thought that the word "Night" was pretty cool and might kind of fit the story. Maybe he just had a publishing date to get to so he just looked outside and said, "Wow, it is dark outside. It's Night and I'm finishing this book. I might as well