One of the big decisions about publishing your book has to do with whether or not you want to release physical copies or simply stick to electronic copies. Once you have decided to print physical copies of your books, you have to decide whether or not you want a dust jacket to be a part of your book or not.
Years ago, when a dust jacket was used, it presented a different cover image that was more elegant and attractive to readers. This was due to the limited functionality of printing presses of the day. In the past, the cover under the dust jacket would be course and imageless. At that time, books were something of a luxury. They were valuable and needed protection, which the dust jacket served to provide quite well. Books also used to be made from fabric which was easier to damage than our modern books made of cardboard, so dust jackets served more of a purpose in that regard as well.
Today, some hardcover books still opt for the elegant and detailed dust jacket, while keeping the hardcover below fairly plain. In other instances, hardcover books use the same cover below the dust jacket as is printed on the jacket itself. So why use a dust jacket at all?
Some authors and publishers may do this to protect the book from heavy use, as in the case of textbooks and manuals which will be passed through many hands. Others opt for dust jackets which can be easily printed in different cultures to target worldwide markets, which is more cost effective than reprinting different hardcover designs for different markets. For example, the excerpts and reviews that you use in Canada may differ from those you want to use when releasing your book in the UK. Prices and currency may vary in this instance as well.
For many, the use of a dust jacket is a tradition that is still useful today. All of these things are considerations that you may want to take into account when deciding upon a dust jacket for your hardcover copy.