When you're on the order page, you will see a Cover option beneath the style of your book. From there you can select between Hardcover and Softcover. This option is only available for the Classic Custom style in the 11x9 and 8x6 sizes. If you have an eligible book style listed but you still don't see the Softcover option, this can be due to text on the spine of your album. Because text on the spine is only available with hardcover, you'd need to go edit your project and remove all text on the spine of your album before you can purchase your book in softcover.