No information is available regarding a US nonprofit organization named "Book Fair" with the EIN 431888560. Therefore, it is not possible to write a Wikipedia-style article about this specific organization based on the search results provided.

[1] https://firstbook.org [2] https://www.lovemylibrary.com/Top-10-book-fair-companies [3] https://www.la-libreria.net/book-fairs/ [4] https://bookfairs.scholastic.com/content/fairs/sponsor.html [5] https://literati.com/bookfairs/