What are the themes of novels about dreams?

Wonderland, beyond dreams, lost dreams, etc.

1, "Wonderland": It describes that the hero enters a fantastic fairyland in his dream and launches an adventure story with various magical creatures and characters.

2. The other side of the dream: It tells the story that the hero came to the other side of a mysterious world in his dream and explored its secrets and stories.

3. "Dream": describes the protagonist lost in a dream, constantly crossing various dreams and looking for a way to return to reality.