Hello,
A couple things I noticed with a cursory look:
Your get_book_list function was trying to return a variable called list. You should try to avoid giving variables the same name as Python’s built-in words. You can see that they show up in blue in the code editor and so that is an indication that they are special words. You could just call it “book_list” instead for example.
The refresh function was not actually being called. Rather than using a custom event to trigger that function, you could just call it directly (e.g., self.refresh_books()).
Does this help?