One of the things people loved about my library-themed wedding were the book decorations we made. Instead of flowers, we had books to decorate and for guests to take home and a book that "fans" out. I don’t know if this is even considered a “DIY” or a craft, it’s so easy to make, and it's even a little therapeutic. All you need is a book, and a great podcast or Netflix show.
We have a few thrifted books we would never read again, and instead of giving them back to the thrift store or even throwing them out, we use them for decoration. For each book, just fold the top corner completely to the spine, go the to next page, and fold the bottom corner to the spine. Simple!