Codex Gigas is a big book from a long time ago that has lots of pages inside. It's so big that it's one of the biggest books in the whole world and it's also really heavy!
This book has lots of different things inside, like stories, pictures, and information about lots of important stuff. Some people call it the Devil's Bible because there's a big picture of the devil inside!
The book was made a long, long time ago - nearly 800 years ago! It was thought to have been made by just one person who wrote and illustrated everything inside. It's really amazing to think about just one person making such a huge and detailed book all by themselves.
The Codex Gigas isn't just important for its size and age, it's also really special because it's written in Latin - a really old language that not many people use anymore. This means it's really rare and special for people who are studying the history of books and reading.
Overall, the Codex Gigas is a really fascinating book that tells us a lot about the way people used to write and think hundreds of years ago. Its size, age, and unique features make it a really special treasure for people who are interested in history, books, and learning!