Both are (or can be) basically relational databases, so you have a table for authors, one for genres maybe, one for physical location, and one for books. You create a new book, and that “form” then gives you fields for Title, Description, Rating, whatever you need, and then pulls data from the other tables for Author, Genre, etc.
If you’re not used to relational databases, the Golden Rule is basically:
If a data type is unique (e.g. Title, Description), it stays with the “product” (book, in your case).
If the data type can be used for more than one item (e.g. Author, Genre), it should (probably) have its own table.
You can take it a step further and make tables for all Descriptions, Titles, etc., and then those get related to the book by a unique key, but this is probably unnecessary for your use case.
All of this is incredibly simplified, and if anyone who works with databases sees it, I’m sure I’ll get corrected 😅
Anyway, you might not need to think too much about any of the above, as both platforms have user contributed templates!