Have you checked there is actually data loaded into your collection?
I have run multiple queries but nothing is returned for either all books or a specific book?
Your screenshot is of the json file in the repository - has this data actually been loaded into your database?
From the code there are a number of process.env variables that need to be set to load the data, these may not be set hence why I asked if the data has actually been loaded into the database.
Can you check if your mongo cluster has the data from the json loaded into it.