// preload cover
if (document.images) {
  var p1 = new Image(188,164); p1.src="/img/book/wrcfacebook-cover.jpg";
  
}
var bookbox_elem = null;
function showCover() {
    if (bookbox_elem==null) {
        bookbox_elem = document.getElementById('bookBox');
    }
    bookbox_elem.className = 'bookBox-cover';
}
function hideCover() {
    if (bookbox_elem==null) {
        bookbox_elem = document.getElementById('bookBox');
    }
    bookbox_elem.className = 'bookBox-normal';
}