The painting mentioned in Morpurgo's author's note is real. Well, kind of. The author's note makes it seem like he was inspired to write War Horse by a painting, but that part is made up. Instead, the painting was made after the movie made the story popular worldwide. (Source.)
In 1997, Morpurgo penned a sequel to War Horse called Farm Boy. It's a multi-generational tale about Albert's descendants, who share stories about Joey. What do you think: does it stand up to the original?
Joey's memory of Albert after months and months of separation isn't the stuff of fiction. Horses have fantastic memories of their human friends and "can hear the human voice better than even dogs can" (source). We've heard that an elephant never forgets, but it looks like a horse could be your true BFF.