CSS to set A4 paper size

Question

I need the option to print this page exactly as it appears in the browser by simulating A4 paper on the web (Chrome, specifically). Despite setting the element size to 21 cm by 29.7 cm, my page is clipped when I send it for printing or run a print preview.

body {
  margin: 0;
  padding: 0;
  background-color: #FAFAFA;
  font: 12pt "Tahoma";
}

* {
  box-sizing: border-box;
  -moz-box-sizing: border-box;
}

.page {
  width: 21cm;
  min-height: 29.7cm;
  padding: 2cm;
  margin: 1cm auto;
  border: 1px #D3D3D3 solid;
  border-radius: 5px;
  background: white;
  box-shadow: 0 0 5px rgba(0, 0, 0, 0.1);
}

.subpage {
  padding: 1cm;
  border: 5px red solid;
  height: 256mm;
  outline: 2cm #FFEAEA solid;
}

@page {
  size: A4;
  margin: 0;
}

@media print {
  .page {
    margin: 0;
    border: initial;
    border-radius: initial;
    width: initial;
    min-height: initial;
    box-shadow: initial;
    background: initial;
    page-break-after: always;
  }
}

<div class="book">
  <div class="page">
    <div class="subpage">Page 1/2</div>
  </div>
  <div class="page">
    <div class="subpage">Page 2/2</div>
  </div>
</div>

I think I'm forgetting something. But what would it be? 
Chrome: clipping page, double-page (it's just what I need it to work) 

Firefox: It works perfectly. 
IE10: Believe it or not, it's perfect! 
Opera: very buggy on print preview

Answer 1

I looked into it further, and the issue appears to be with assigning initial to page width under the print media rule. If no specific length value is defined for width on any of the parent elements (width: initial in this case resolves to width: auto... but actually any value smaller than the size defined under the @page rule causes the same issue), it appears that in Chrome width: initial on the.page element results in scaling of the page content.

So not only is the content now too lengthy for the page (by around 2cm), but the page padding will be slightly greater than the initial 2cm, and so on (it appears to render the contents under width: auto to 196mm and then scale the entire content up to 210mm, but curiously, the same scaling factor is applied to contents with any width smaller than 210mm).

To resolve this issue, just set the A4 paper width and height to html, body, or straight to.page in the print media rule, avoiding the beginning keyword.