Apple has released a minor update to their iBooks application, 1.1.2. From what I can tell, the update has been released to address an issue that some customers were having installing the iBooks 1.1.1 update that was released just a few days ago.
You can download and install iBooks 1.1.2 on your iPad with iOS 3.2 and iPhone or iPod touch with iOS 4.0 or later installed. Hit the App Store icon on your iDevice or use the iTunes on your Mac or Windows PC to download the update.