1. The Davinci Code is the most exciting book I've ever read.
2. The Da Vinci Code is the most exciting book I've ever read.
(Which title is right? Can we omit 'the'?)
The complete title is this: The Da Vinci Code. You cannot omit The.
The title of this book is The Da Vinci Code.
Both sentences are correct, but there is a difference in the capitalization of the title. The correct title of the book is "The Da Vinci Code" with a capital "T" in "The" and a capital "D" in "Da Vinci Code."
As for the second question, whether or not you can omit "the," it depends on the context. If you are referring to the specific book titled "The Da Vinci Code," it is important to include the definite article "the" before the title. However, if you are talking about the general concept or genre of Da Vinci Code-like books, then you can omit the article. For example, you could say, "I enjoy reading Da Vinci Code-style books" without using the definite article "the."