Dr. Seuss is a classic American icon. Whimsical and wonderful, his work has defined our childhoods and the childhoods of our own children. The silly, simple rhymes are a bottomless well of magic, his illustrations timeless favorites because, quite simply, he makes us laugh. The Grinch, the Cat in the Hat, Horton, and so many more, are his troupe of beloved, and uniquely Seussian, creations.

Theodor Geisel, however, had a second, more radical side. It is there that the allure and fasciation of his Dr. Seuss alter ego begins. He had a successful career as an advertising man and then as a political cartoonist, his personal convictions appearing, not always subtly, throughout his books—remember the environmentalist of The Lorax? Geisel was a complicated man on an important mission. He introduced generations to the wonders of reading while teaching young people about empathy and how to treat others well.

Agonizing over word choices and rhymes, touching up drawings sometimes for years, he upheld a rigorous standard of perfection for his work. Geisel took his responsibility as a writer for children seriously, talking down to no reader, no matter how small. And with classics like Green Eggs and Ham, and One Fish, Two Fish, Red Fish, Blue Fish, Geisel delighted them while they learned. Suddenly, reading became fun.