What is the difference between plagiarism and copyright infringment? Plagiarism is presenting someone else’s work as your own. Copyright is the author’s right to reproduce an original work of authorship. Plagiarism is enforced by schools and academics; Copyright is enforced by courts. While copying The Da Vinci Code and publishing the copy as your own, would be both plagiarism and Copyright infringement, the two do not always overlap.
For instance, if you copied the Bible and presented it as your own, that would be plagiarism, since it involves claiming credit for something you did not do. This might get you kicked out of school, but would not constitute illegal copyright infringement, since there is no copyright on the Bible. Conversely, incorporating large, properly cited, excerpts from The Da Vinci Code in your own novel, would likely not constitute plagiarism, since you are not claiming the work as your own, but could constitute copyright infringement, since you are reproducing the copyrighted work without permission.
Plagiarism and copyright infringement both, however, require proof of access. The similarity between the original and accused books often circumstantially proves the second author had access to the work of the first. If you could prove that you had been trapped in a cave for the last ten years, with no access to the outside world, and that you coincidentally came up with The Da Vinci Code word for word, you could, ostensibly get your own copyright on the book and sell copies. This would not constitute either plagiarism or copyright infringement.