Unfortunately, you can't transfer photos from one ideabook to another per se. Go to the photo that you'd like to move, and save it to your other ideabook, just like you would save any photo. Then you just delete it from the ideabook that you want to remove it from. Do this by going into the ideabook and clicking the "edit" box. Then when the ideabook comes up in edit mode, just click the "x" by the photo to delete it.