The cover of a book, especially an antique, determines its value. A great volume with an intact spine and flyleaves is sought-after by collectors the world over.
When you make a book, keep in mind that the cover is not an afterthought. It is not simply a holder for the title or something to keep the pages inside from getting ruined. Yes it is all that too but it's more.
It's like the front door. It's the readers first interaction with your work. It's the thing they hold and manipulate to get to the "good stuff." It's the first stop on a journey through your work. Why not make it really count?
An article to enjoy is this one on an exhibit of the Morgan Library and Museum. A limited collection of their books spanning 1400 years displays the exquisite detail of the covers. You almost hate to open them up for fear the text won't live up.
When you maker your next book I hope you will take the opportunity to make the cover a work unto itself.