#ebookPopup {
    display: none;
    position: fixed;
    z-index: 9999;
    background: rgba(0, 0, 0, 0.75);
    top: 0; left: 0;
    width: 100%;
    height: 100%;
}

#ebookPopup .popup-content {
    position: relative;
    background: #fff;
    width: 80%;
    max-width: 900px;
    margin: 5% auto;
    padding: 10px;
    border-radius: 8px;
}

#ebookPopup .close-btn {
    position: absolute;
    top: 10px;
    right: 15px;
    background: #f00;
    color: #fff;
    border: none;
    padding: 5px 10px;
    cursor: pointer;
    border-radius: 3px;
}

#ebookPopup iframe {
    width: 100%;
    height: 600px;
    border: none;
}