div.book-cover {
    border: 1px solid #efefef;
    float: left;
    height: 250px;
    margin: 0 7px 15px 0;
    padding: 5px;
    width: auto;
}

    div.row-last { margin-right: 0; }

    div.book-cover:hover { border-color: #ccc; }