A book cover is representational of the contents of the book of which it is covering. It uses imagery, colors, and specific font to make a statement and grab-attention.
Watch the video on "Book Covers" to learn more.
You will need to consider design elements such as font choice, color palette, use of space and illustration, as well as content and imagery. You may use a free version of any of the programs listed below. Also, be sure to select a free template and not a premium template when creating your design: