My Lists allows you to keep track of books and other materials in the Library collection. A list is a collection of titles related to a specific topic or idea of your choosing.
You can find more information about My Lists here: https://help.bibliocommons.com/045faq/060faq-lists/
My Shelves gather in one place all the titles you have read, watched or listened to (Completed), are currently enjoying (In Progress) or would like to borrow in the future (For Later).
You can find more information about My Shelves here: https://help.bibliocommons.com/045faq/040faq-my-shelves/