Unfortunately, there isn't a "one click" answer to this question. First you will need to go into the ideabook that has the photo you want to move, then you will simply need to click on the "add to ideabook" button for that photo and when the dialog box comes up you will add it to your new ideabook. Then to remove the photo from its original ideabook, you will choose the "edit ideabook" option and remove the photo from the book.

Hope this helps.