Amazon offers The Captain Underpants Colossal Color Collection (Captain Underpants #1-5 Boxed Set)  for with free shipping.

Product Description:
Laugh out loud with Captain Underpants, the #1 New York Times bestselling series from Dav Pilkey, the author and illustrator of Dog Man!
Meet George and Harold, two fourth graders with BIG imaginations. The only thing they enjoy more than playing practical jokes is creating their own comic books about a superhero named Captain Underpants. But nothing can prepare them for what happens when their comic-book character comes to life!This boxed set -- perfect for fans and newcomers alike -- includes the first five Captain Underpants books in full color, which feature Flip-O-Ramas, mini comics, and fun facts! There's never been a better time to add to your Underpants collection!