The two ways good covers still fail
Both are avoidable and both are common.
It signals the wrong genre
Genre conventions are how a browsing reader works out what your book is before they read a word. Type, colour and imagery all carry that signal. A literary looking thriller confuses exactly the people most likely to buy it. We work from this year's bestseller grid in your category, not from covers that were current a decade ago.
It wasn't built to the printer's template
A print cover is one spread across back, spine and front, built on a template generated from your final page count and paper stock. Spine width is arithmetic. Get it slightly wrong and the title sits off centre on every copy that ever prints.