The answer to this question largely depends on which writing style or format you're using for your book titles. Generally, there are several occasions when it's appropriate to use the definite article 'the' in book titles:
• To refer to books as part of a series: For example, The Lord of the Rings by JRR Tolkien
• To refer to a single work of multiple distinct parts: The Collected Works of William Shakespeare
• To refer to a unique object, person, or place: The Catcher in the Rye by J.D. Salinger
• To refer to books specifically by title: The Adventures of Tom Sawyer by Mark Twain
In general, titles of books should follow the rules of English grammar as closely as possible. If you're uncertain as to whether or not you should use the definite article 'the' in a book title, it's best to consult an English grammar guide. Additionally, you may wish to consult an editor or the publisher of the book if you have any questions.