PETA won’t be pleased.

Animal rights activists’ favorite fur-wearing celebrity sibs are seeking to expand their literary franchise with the publication of a new book for kids.

With their coffee table book Influence flying off the shelves of booksellers’ across America, Mary-Kate and Ashley Olsen have decided to once again put on their author caps and pen another national bestseller.

The mini-moguls are diligently working on their first children’s book, based on none other than the subject they know best-twins!

“Mary-Kate is doing the illustrations, while Ashley is coming up with the story,” a friend reveals to Star. “They’re hoping to do an entire series based on this concept.”