.book {
    padding: 15px 0 0;
    margin:auto
}

.shelf {
    border-bottom: 30px solid #a5a5a5;
    border-left: 20px solid transparent;
    border-right: 20px solid transparent;
    top: -20px;
    z-index: -10;
    margin-bottom:50px
}

.shelf:after {
    content: '';
    background: url(../img/concrete_bg_dark.jpg) top left repeat-x #686868;
    height: 20px;
    width: calc(100% + 40px);
    position: absolute;
    top: 30px;
    left: 0;
    right: 0;
    z-index: 1;
    margin: 0 -20px
}