Design elements should be carried throughout the book
Since my site is mainly one for book cover design, I work with a lot of clients who come to me for just that one element of the book.
There is no problem with this, but I like to at least make contact with the interior designer, or if that part of the job is already done, see the finished product. This is so I can create a cohesive look that carries from front cover, through every page and onto the back cover.
The fonts you’ve used; any graphic elements, such as dingbats or lines; drop caps or other features used on the books interior can be mirrored on the cover, and vice versa.
This is not always possible of course, sometimes covers change for various reasons, but the interior of the book stays the same. One good example is once a movie has been made about the book, a new cover will immediately be produced that reflects the move characters and title, but quite often the interior is not altered.
Book Cover Express has a wonderful, very experienced interior designer and through the years we’ve formed friendly working relationships with many others. Collaboration is not usually an issue.
One problem I do run into is with do-it-yourselfers who are creating very amateurish interiors, using Times and Ariel, mixing too many fonts, not spacing paragraphs properly and not understanding punctuation (there is a difference between a hyphen, an em dash and an en dash). Since the cover is the handshake that greets the world, you can’t really afford to display anything that’s no able to hold its own in a competitive world with professionally-designed books.
Try to remember your book is one project and it should have a distinctive look that identifies it throughout.