Hey there SE site!
I have a couple of suggestions for you that can help you resolve this issue. First, you will want to just try deleting the book and downloading it again. I have an article that can give you more information on downloading past purchases right here:
Downloading past purchases from the App Store, iBookstore, and iTunes Store
http://support.apple.com/kb/ht2519
Alternatively, if you are still seeing issues with your book after attempting to delete and redownload, you will want to report this issue to iTunes so they can look into it. The link for more information about how to do that can be found here:
How to report an issue with your iTunes Store, App Store, Mac App Store, or iBookstore purchase
http://support.apple.com/kb/ht1933
Hope this helps. Thanks for using the Apple Support Communities!
Cheers,
Braden