I rarely use iBooks except for checking ebooks I've designed, so this problem may be old news to some people.
The latest ebook I uploaded uses the following XHTML and CSS to centre images:
<div class="centre">
<img src="images/valid.png"
width="25%" alt="valid html, css, and epub" />
</div>
.centre { text-indent: 0; text-align: center; }
It has worked perfectly well to centre images on an iPad2 in the past, and worked perfectly well tonight on my Sony PRS T3, a Kobo Touch, iPad mini with Marvin, Nexus 7 with Mantano, and upgraded Kindle Keyboard. But on an iPad mini the images are flush with the left margin - not centred at all.
Has anyone else seen this problem? Is it a problem with an iPad mini? Or iOS8 and the latest version of iBooks? I can't believe it's because of my markup and CSS since they worked in the past and work on other ebook readers.
Perhaps more importantly: is there a way to centre images with this combination (iPad mini, latest iBooks, and iOS8) that will also work on other ebook readers?
I should mention perhaps that an image which is floated right and has text wrapped around it still works on the iPad mini. And the CSS still centres text material on an iPad mini.
If you need to check the markup and the CSS the book is
Right at Last and Other Tales by Elizabeth Gaskell.