Q: I just downloaded a book from ibooks and it says that it is unable to open the book

Hello, jbc1952. 

Thank you for visiting Apple Support Communities.

I would recommend deleting the problematic book and downloading it again by accessing your previous purchases.  Here are a couple articles that will help you with this process.

iPhone, iPad, or iPod touch

Before you delete, find out if you'll be able to download the book you deleted again (it depends on where you live). To delete a book:

1. Tap the iBooks app.
2. View your Purchased Books collection.
3. Tap Edit.
4. Tap any books you want to delete.
5. Tap Delete.

You'll have the option to delete your book on all your devices.

How to delete content you've downloaded from the iTunes Store, App Store, iBooks Store, or Mac Apphttp://support.apple.com/kb/HT5772

Books

Follow these steps to download purchased books:

1. Tap iBooks and tap Store.
2. Scroll down and tap Purchased.
3. Tap the book that you want to download.

Download past purchases

http://support.apple.com/kb/ht2519

Cheers,

Jason H.