It's very important. The back cover gives an overview that can attract or repel potential readers. It can set the tone for what to expect in the book, like if it's a mystery, the back cover might give a tantalizing clue.
One way to tell is by checking for references or sources mentioned. Also, see if the language and tone are objective and based on facts rather than pure emotion or speculation.
The back cover of a novel is sometimes called the 'backside cover'. It plays an important role in providing additional details about the book to attract readers, such as a brief description of the plot or praise from other authors.
NPR likely covered the Unabomber's back story by interviewing experts on criminal psychology. They may have also talked to people who knew Ted Kaczynski personally, like former neighbors or classmates. By gathering these different perspectives, NPR could piece together a more complete picture of his background, from his early days as a bright student to his descent into becoming a serial bomber.
For the front cover, having a unique and artistic design is a good start. For example, if it's a mystery short story, a shadowy figure on the cover can be alluring. The font of the title can also be creative. As for the back cover, a well - written summary that builds suspense and doesn't give away too much is key. Also, including some positive remarks from early readers or reviewers can boost its attractiveness.