The iBookstore now has support for screenshots and promo codes, according to an iTunes Connect letter that was sent to content publishers today and that TUAW obtained. Content publishers are now able to giveaway 50 free codes that redeem a copy of a book they are selling on the iBookstore — something developers on the App Store have long been able to do. No doubt it will be helpful for publishers trying to get their books reviewed and for when they want to run promotional give-aways.
The other big change is that publishers can now also submit screenshots of the book. This new feature will be most useful for multi-touch books that are created with the iBooks Author app. Like the App Store, Apple is specific about the dimensions and formats it will accept for this: 1024 x 768 or 768 x 1024 in RGB, formatted as either .jpeg, .jpg or .png.
Apple has also made a minor change to how pre-orders are handled on the iBookstore. From now on, publishers need not upload a cover or any other assets until two weeks prior to publication, but can still offer the product for pre-order.