The only thing that limits our knowledge is ourselves, "less constrained than in a library" implies that a library is a limitless opportunity for knowledge. You could pick up any book and learn something from it. In this way, the library has more opportunity for learning and creativity than somewhere compared to, say a forest, where you're limited to the knowledge you gain from experiences or prior knowledge.
The 5th way an author uses to describe a character is through speech.
Explanation:
Author's use speech as another way to describe a character because in a story you need dialogue and dialogue is speech, thus meaning the 5th way to describe a character is speech.
