This is one of my very favorite knitting books! The colors and designs are gorgeous, the format is pleasing, and I just love to look at the pictures for color inspiration. I am a somewhat experienced knitter, I love knitting in the round (no seams to sew after the project is finished!) and I love to make colorful hats, which I sell at crafts fairs, so for me it's a perfect book. All the designs use worsted weight yarn and #7 or 8 needles, so the hats knit up fast.
I agree however that it's not ideal for knitting beginners, although with hands-on help from a more experienced knitter it should be possible. I have come across some minor errors - another reason it's more appropriate for non-beginners.
But otherwise I highly recommend it to anyone looking for fun, colorful, fast knitting projects. I make them for my friends, who love them. As Anna says in her introduction, you're doing the world a favor when you make these hats, because they make people smile!