I had this problem with one book as well, MamaSue. My solution for that book was to load the book through Calibre, which worked. I believe that it was a malformed book that "landed" in the database, but did not have the coding to actually interact the right way with the reader.. Even when sideloaded through Calibre the book was very, very slow to load--annoyingly so. One choice, if you are not wanting to go the Calibre route, would be to write to
help@kobobooks.com and ask for a refund.
If you do use Calibre, think of it as you would ADE and just import the book from your "My Digital Editions" folder on your computer into Calibre or download the ePUB again, using Calibre rather than ADE as your download program, when asked your preference. I am guessing that the original download will show up in the new version of Calibre and that you can delete it from there (click on device===>show books in main memory==Choose delete).
My experience was that having the *bad* book in the Db screwed with how "I'm Reading" worked on the Kobo and getting rid of the book in the sqlite Db solved the problem. It may just be a coincidence, but that was how it worked for me. Back then, there was no option to remove the book through Calibre so I decided to use a recent backup of my sqlite file--had I not had one, I think I would have seen if replacing the Db would have worked or reset to factory defaults and reloaded the books.