Many authors get an ISBN number mixed up with a barcode. A unique ISBN number is necessary (although you may not need to purchase one as discussed below). A barcode, on the other hand, is only necessary if you are distributing a physical or printed copy of your title. So the basic answer to the question of whether you need an ISBN is yes. However, there are many reasons why you might not want to buy an ISBN at this point. First of all, doing so will not prevent others from using your work illegally. It is also very expensive. Finally, an ISBN is useful for more than just preventing copyright infringement. For example, it can be used by libraries to identify books they carry. So even if you aren't planning to distribute any copies of your book, there are good reasons to get an ISBN. The first thing to understand is that an ISBN is not a barcode. An ISBN is a unique numeric code that identifies a particular edition of a book. The ISBN identification system was created by the International Standard Book Numbering System (ISBN) Board. They define an ISBN as "a 10-digit linear bar code used to uniquely identify a published volume." That means that while a barcode is a useful tool for identifying products, it's not suitable for identifying books. If you look at a book on Amazon, for example, the product page will list various properties about the book, including its dimensions, weight, and price.