How can I read a book via iBooks on my mac?

I bought a book from iTunes many years ago for my iPhone 3. I know have an iPhone 4s. Between the switching of phones and updates throught the years, I had lost my books in iBooks. I just recently re-downloaded the app, "iBooks" on my MacBook Pro and found the book in iTunes which I had purchased years before. So I opened the book in iBooks on my Mac but when I tried to actually open the book to read, and error keeps popping up saying, "Book can not be opened. Book is corrupt." I have no idea what that means how how to fix it, but since I purchased the book years ago, there isnt an option for me to Re-Buy it. Anyone know what this means or how to fix it? Thanks!