Unable to download and read selective books (iBooks)

Recently I had to restore my iPad Mini (1st gen) from an iCloud backup. I didn't lose any data since I back up regularly. Unfortunately, not all of my ibooks are downloading nicely. Here is a rundown of what I am doing:

1. I open ibooks
2. I click on the "download" icon for the book I want to download (currently only two out of the two-dozen or so books I've purchased are giving me this problem)
3. The "downloading bar" begins to fill as if the book is downloading
4. The bar fills
5. The download icon reappears and when I click the book again, the whole process begins again at step 3.

This repeats over, and over, and over again. I decided to try and download more purchased books and so far, I've only had this problem with two books.

Any ideas on how I can fix this?