Buy the book here.

Nothing says holiday cheer better than a brash Christmas sweater—and the uglier, the better.

Ugly Christmas sweaters come in many shapes and sizes, from classic, vintage styles that would make the Griswolds proud to high-tech numbers with blinking LED lights and sound effects. With ugly-Christmas-sweater parties becoming increasingly popular around the world, some folks are even engaging in an arms of race of ugly, to see who can boast the most festive flare, without causing car wrecks.

Many of the best of the worst ugly sweaters are collected in the new book 'Rock Your Ugly Christmas Sweater,' which features more than 200 photos of people and pets in hilarious holiday finery, from ugly vests to sweater dresses, jackets and much more. Many of the most outrageous numbers came from the site My Ugly Christmas Sweater.

Remember: It's hard to have a bad time when you are wearing an ugly Christmas sweater.

See more funny photos (and upload your own) at Rock Your Ugly Christmas Sweater.

Jason Yormark / 'Rock Your Ugly Christmas Sweater'
ZacFisherPhoto.com / 'Rock Your Ugly Christmas Sweater'
Alli Valentine / 'Rock Your Ugly Christmas Sweater'
Anne Marie Blackman / RockYourUglyChristmasSweater.com
Brian Clark Howard / RockYourUglyChristmasSweater.com
Anne Marie Blackman / RockYourUglyChristmasSweater.com
Anne Marie Blackman / RockYourUglyChristmasSweater.com
Anne Marie Blackman / MyUglyChristmasSweater.com
Anne Marie Blackman / MyUglyChristmasSweater.com
Anne Marie Blackman / RockYourUglyChristmasSweater.com