Green Eggs and Ham is a children's book by Dr. Seuss, first published on August 12, 1960. As of 2019, the book has sold 8 million copies worldwide. Green Eggs and Ham is one of Seuss's "Beginner Books", written with very simple vocabulary for beginning readers. The vocabulary of the text consists of just 50 words and was the result of a bet between Seuss and Bennett Cerf, Dr. Seuss's publisher, that Seuss (after completing The Cat in the Hat using 236 words) could not complete an entire book without exceeding that limit.

Source: Wikipedia