It should not be much more than 500 words long. Theodor S. Geisel (aka Dr. Seuss) wrote “Green Eggs and Ham” after his publisher, Bennett Cerf bet him $50 that he couldn’t write a book using only 50 words. The Cat in the Hat is only 225 words long. Go take a look at either book. You probably thought there were a lot more words.
A picture book must include pictures. Since most picture books are 32 pages long that means there must be at least 14 pictures. That’s not rule #2 though. The second rule is that the story should not describe the pictures and better yet, should not even mention them.
Those are just a couple reasons why “Writing a picture book is like writing ‘War and Peace’ in Haiku.”