iframe.book {
    width: 100%;
    height: 100vh;
    border: 0;
    position: fixed;
    top: 4em;
    left: 0;
}

.bd-sidebar {
    border: none;
}

/* we need to put z-index low otherwise we obscure the navigation sidebar for the books */
.bd-sidebar.no-sidebar {
    border: none;
    z-index: 0;
}

/* we need to put z-index low otherwise we obscure the navigation sidebar for the books */
.bd-toc {
    z-index: -10;
}

/* better layout of title */ 
.navbar-brand {
    padding:0.9rem 0;
}