An epistolary novel is a special kind of story where the whole thing is made up of letters! You know how sometimes you write letters to people you love, like your grandma or your best friend? In an epistolary novel, the whole story is like that. It's made up of letters that characters write to each other.
So instead of the author telling us about what's happening, we get to read the letters the characters are sending back and forth. It's really cool because we get to see the story through their eyes and learn about what's happening through their own words. Sometimes, there might even be letters from different people that show us different perspectives on the same event.
Epistolary novels can be really fun to read because they feel like a secret peek into someone else's life. They're kind of like getting to read someone else's diary, but it's okay because they want us to read it!