Living is what people do every day, it is simply the act of being alive. Surviving is more related to going on after something has happened, like when a person dies, they "are survived by" e.g. their children, or someone was in a car crash and they survived. They have lived through something as opposed to simply being alive.

Also, having zero interest in HP I couldn't say as to the specifics in your case, but it sounds like perhaps it is implying there was an incident where this boy lived and others did not... So in that case it seems like the title would be putting the emphasis on the fact that this one boy stayed alive. Without specific context it can be hard to say, but especially when you are talking about books, authors will play with language more subtly and nuanced than general speech and whatnot.