So imagine you really like hearing stories about heroes - people who were really brave and did exciting things. Well, that's what a heldenbuch is - it's a book full of stories about heroes.
These heroes might be real people from history, or they might be made up characters that someone has written about. But either way, the stories are all about things that these heroes did that were really impressive.
Sometimes the stories are about battles, or adventures they went on. Sometimes they're about how the heroes stood up for what they believed in, even when it was hard. And sometimes they're just fun stories about how these heroes used their cleverness to outsmart their enemies.
One thing that's really cool about heldenbuchs is that they've been around for a really long time. People have been writing and reading these kinds of stories for hundreds of years! And even today, people still love reading and hearing stories about heroes.