First, they've disable the right click, so you can't capture the image of the page. But even better, if you try to print, the page image disappears (and leaves a very odd-looking display as a result). The relevant code in their page appears to be:
<style type="text/css" media="print">
.readerImage {
display:none;
}
I admit I don't really understand how this works, but the simplicity of it intrigues me. I've been playing with it in a saved copy of the page. I assume it simply doesn't load the image when the print function is selected. The same thing happens during print preview (well, at least that's honest).