Today is the 19th Day of Advent and we’re highlighting a couple of excellent science books today! From 9:00am to 7:00pm today only, An Earthling’s Guide to Outer Space by Bob McDonald and Randall Munroe‘s How To will be 20% off! Perfect for the science buffs on your Christmas shopping list, be sure to take advantage of this one-day sale so you can cross a few more things off your holiday to-do list!