Many Duplicate Pages Within A Book.

I just opened an ebook on my hard drive and calibre picked it up and imported it to calibre within which I set off to view it.

I found each and every page to be duplicated twice.

I move right to the next page and it is the same as the one I just left.

Then right to a new page, then right again to another duplicate and so on..

It's the same coming back, two pages for each page.

How can I fix that?