I have noticed that with some books. For most of them, when I look at the content, I find that for some reason that I can't wrap my mind around, the last lines of the text are blank lines. This can also happen when a margin-bottom is used to give space between paragraphs which is why I prefer a padding-top. Sample from one recent book:
Code:
<p style="margin:0.00% 0.00%; text-align:center; widows:0; orphans:0"> <span style=" font-size:1.25rem"> </span> </p>
<p style="margin:0.00% 0.00%; text-align:center; widows:0; orphans:0"> <span style=" font-size:1.25rem"> </span> </p>
<p style="margin:0.00% 0.00%; text-align:center; widows:0; orphans:0"> <span style=" font-size:1.25rem"> </span> </p>
<p style="margin:0.00% 0.00%; text-align:center; widows:0; orphans:0"> <span style=" font-size:1.25rem"> </span> </p>
<p style="margin:0.00% 0.00%"> </p>
</div>