This is a question that very few people think about. The natural reaction to the question, “What is the New Testament?” is that it is a collection of books in the Bible.
But before you say the New Testament is “a book” ask yourself what the book says the New Testament is. A hint is found in Luke 22:20 and 1 Corinthians 11:25. In this verse the words “testament” and “covenant” are synonyms (see KJV and Douay-Rheims).