In its first week on sale, What Pet Should I Get?, the new book by Dr. Seuss, sold 200,000 copies, making it the fastest-selling picture book in Random House Children’s Books history.

“We are so pleased with the tremendous sales for What Pet Should I Get? across North America, and the reports from many booksellers that it was their biggest-selling title, adult or children’s, last week,” said RHCB president and publisher Barbara Marcus. “This picture book treasure now sits prominently among the fastest selling picture books of all time—and we couldn’t be prouder to share it with readers everywhere.”

The book, which went on sale July 28, also made history at retailers. On July 30, Books-a-Million announced that What Pet Should I Get? set a company record for best first-day sales for a children’s picture book.

In addition, RHCB announced that it would be teaming with Dr. Seuss Enterprises on a social media campaign that will support the work of the ASPCA to help animals in need across the country. The campaign celebrates the author's "love for animals," the publisher wrote in a statement, and calls for all pet owners nationwide to share a photo of their pets, tagging it with the #whatpet campaign hashtag. For every photo shared on Twitter or Instagram with #whatpet, RHCB and Dr. Seuss Enterprises will donate one dollar to the ASPCA, up to the first 15,000 photos.

RHCB first announced the book in February, after the rediscovery of the full text and illustrations for the work in the office space of the late author.