Joel Friedlander said this quote

“ There are a lot of conventions, a vocabulary and a set of practices and assumptions that underlie most professional book design. Since design is important to the eventual success of your book whether you attempt to do it yourself or hire it out, it pays to know something about those conventions and assumptions. After all, we don’t want anything getting in the way of your communication with your readers. You’ve got a message for them, a story to tell, or ideas to spread. That’s what’s important. ”