My view may be simplistic, but it is this: novels engage the reader by telling stories. An ambiguous end to a novel is not a problem -- ambiguity is fine. In fact, it may be the most truthful way for a novel to end.
Harry Potter is now the most banned book in America, according to the American Library Association. But these books have taught children to read, to think, to write and to criticize, all hallmarks of free expression.