I've done several snapfish photobooks, my recommendation is to change the page layout. Even if you are using the autofill/auto-create program that snapfish has, you are not tied to the recommended page layout so change it until you find one that fits the photo that you have. I had a really odd shaped panoramic photo that I wanted to use, I had to try about 5 different layouts until I found one that worked to show the whole photo.
If you still can't find a layout that fits, another thing that you can try is to use an outside photo editor to change the shape of your photo but this is not as easy. If you have one such as photoshop you can create a digital photo collage that is the same size as your photobook pages (8x11, 8x8, 12x12,etc.), put in the photos you want for that page, save the collage as a jpeg file, upload the collage to snapfish, then change the layout you are using for that particular page to be one photo per page and choose the full page photo option.
You could try changing companies, but just be aware, that if the problem you are having is because you have an odd size photo you may well never find a page layout in a standard book that fits the photo. Even if you change to a different company such as shutterfly or picaboo (well, with picaboo, maybe, but I have to admit, I find them difficult to use and without a really good coupon too pricey to be worth it.)