Chicago style offers a few different ways to format titles of books.
The first is using italicized text, which is done by capitalizing the first letter of each word in the title and putting the entire title in italics. For example, if the title of your book is The Catcher in the Rye, it would be written as The Catcher in the Rye.
The second way to format book titles in Chicago style is to put them in quotation marks. This is similar to the italicized style, but instead of the entire title being in italics, only the title and subtitle of the book are placed in quotation marks. For example, The Catcher in the Rye would be written as "The Catcher in the Rye".
Finally, if the book being referenced is part of a larger work such as an anthology or collection, the title of the book should be written in roman type, and in quotation marks. For example, if the title of the anthology is The Norton Anthology of English Literature, and the book being referenced is Pride and Prejudice by Jane Austen, it would be written as "Pride and Prejudice" in The Norton Anthology of English Literature.
Ultimately, the best way to format book titles for a Chicago Style paper is to refer to the Chicago Manual of Style for direction on which style to choose.