\version "2.14.2"

\paper {
  % print-all-headers = ##t
  print-all-headers = ##f
}

\book {
  \header {
    title = "Book Title" % this doesn’t show, regardless of print-all-headers
  }
  \bookpart {
    \header {
      title = "Book Part Title" % this always shows
    }
    \score {
      \relative c' {
        c4 c c c
      }
      \header {
        title = "Score Title" % this doesn’t show unless print-all-headers
      }
      \layout {}
    }
  }
}