The book "Horse Heroes: Stallion by Starlight" is a part of the Magic Tree House-Fact Tracker series and is authored by Natalie Pope Boyce and Mary Pope Osborne. It is a nonfiction picture book focusing on animals, specifically horses, and is aimed at young adults and children aged 4-12. The hardcover book, signed by Mary Pope Osborne, features illustrations by Sal Murdocca and has 128 pages. Published by Random House Children's Books in 2013, it explores the topic of equestrian sports and recreation in an engaging and informative narrative style.