.book-header {
    padding: 0;

    position: fixed;
    top: 0;
    left: 0;
    right: 0;

    background-color: #FFF;
    border-bottom: 1px solid @header-border;
    .transition(left @sidebar-transition-duration ease);
}

.book {
    &.with-summary {
        .book-header {
            left: @sidebar-width;

            @media (max-width: @sidebar-breakpoint) {
                left: 0;
            }
        }
    }
}