I made my snowman out of 3 paperbacks that I carved into half circles.
You have to leave the top and bottom edges of the book flat so that you can stack them.
I made a half circle template of poster board for each book, sizing down for each.
I removed the front and back covers for each book, and drew my template on the front page (remember to leave some of the top and bottom flat!) Using scissors, I cut about 6 or 7 pages at a time. Then I repeated drawing and cutting until I was finished with the book. You can cut more at a time with a craft knife, but I found I got jagged pages and it really dulls your blade quickly. The pages sometimes didn't come out the same size because of how the book lays, so I would just trim to match the others as needed.
When you're finished cutting, fold the book back to bend the spine. First halfway, then each half to loosen up the spine. Then I used Scoretape (or any heavy duty double sided adhesive) to adhere the spine to itself when folded back. After that, glue the front and back pages together using a glue stick.
You'll need to "fluff" your book out by turning several pages and and running your hand down the crease like you do when your reading.
I didn't attach my books to each other for storage reasons, but it would be more stable if you hot glued them in the center at the spines. I hot glued some twigs for arms and added a hat and scarf!