Tirant lo Blanch is a very old book that talks about knights and their adventures. It was written in a language that not many people use anymore called Catalan. Think of it like talking in a secret code that only a few people understand.
The book is about a knight named Tirant who goes on lots of exciting adventures, like rescuing princesses and fighting dragons. It's kind of like a really cool story or a movie that you could watch.
But the book is also important because it was written a long, long, long time ago - around 600 years ago! That's older than your grandparent's grandparents! People still like to read it today because it's a really good story and it tells us a lot about what knights were like a very long time ago.