"The Book of the Grotesque" is a preface to the book of short stories Winesburg, Ohio. This book, written to the memory of Anderson's mother, explored the superficiality of life, the convenient way in which people adapt philosophies and constructs, and about what is the truth, according to each and everyone of us.
Due to the nature of the book, "The Book of the Grotesque" served as a wonderful prefatory introduction because it tells the story of a writer who imagines what happens to people when they adopt a "truth".
It was the truths that made the people grotesques. The old man had quite an elaborate theory concerning the matter. It was his notion that the moment one of the people took one of the truths to himself, called it his truth, and tried to live his life by it, he became a grotesque and the truth he embraced became a falsehood.
In the writer's mind, when people adopt a truth, they twist it to their convenience and make the truth no longer pure, nor the way that it is meant to be. Instead, the truth becomes a cartoon version of itself; a grotesque. Similarly, those who live by their crooked versions of "truth", "morality", and "religion", become as grotesque as the truth itself has become a grotesque of it. This is the reality of life: none of us can claim to live in truth.