Simplify the following text for a Grade 7 native English-speaking person.
Original: As one of the most popular children 's authors of all time , Geisel 's books have topped many bestseller lists , sold over 222 million copies , and been translated into more than 15 languages .
Simplified: Theodor Seuss Geisel is one of the most popular children 's authors of all time . His books have sold over 222 million copies and been translated into more than 15 languages .