The generous 3.5" ribbing allows you two ways to wear the hat.
Ribbing turned up:
Ribbing turned down:
Although the book was written for Cascade 220 yarn, based on this and other projects I've knitted from this book, I think any worsted-weight yarn will do.
I used Plymouth Yarn Company's "Encore Colorspun" in colorway "Drifting," a heathery light oatmeal shade. Encore is my go-to yarn when I want to use a nicer acrylic than what I often find in the big craft stores. It's 75% acrylic and 25% wool; you can still machine wash and dry like other acrylics, but the wool addition gives it a softer feel.