Recommended image specifications. Please help?

Question

Hello all.
Could anyone please enlighten me to the best practice image specifications for Multi-Touch books made through iBooks Author? I've looked through the iBookstore Asset Guide and iBooks Author support but can't find anything that specifically applies to .iBooks, just EPUBs. I see that, there, the maximum is 2 million pixels, but does this still apply to .iBooks?
The iPad with Retina's resolution is 2048x1536 (over 3 million pixels), so surely it wouldn't make sense to restrict iBook images in such a way?
Any knowledge welcome.

Answer 1

There could be better verbiage, I agree.
In iBooks Author, the first page is captured and used as the 'cover' automatically when using it's Publish to the store menu, then handed off to iTunes Producer, where you can use it as-is, or change to something else if you desire. If you change it, you need to be aware of the specs (see blurb below)
If you create a standard epub, say from Pages, and then use iTunes Producer, adding cover art is manual.
From iTunes Producer:
These finer points for covers are covered in multiple areas, ranging from several existing threads here to the blurb to the iTunes Producer Guide to Apple tech notes, and this email from Apple last year which the helpful Apple staffer doubtlessly quoted:
Cover Images
We are changing the minimum size for cover images. Cover images should now be 1400 pixels wide, in the RGB color space, and delivered as JPEG files. The new minimum size for cover images will be a requirement starting this August. Books already available on the iBookstore do not need to be redelivered.