It's pretty hollow.
I searched on "maps". It says "All books: 647. Books to read now: 9".
Another obscure inquiry - "britannica" - gives me 98 books, with 1 available now.
But to mitigate, if I click on one of the unavailable books, it says:
This book has not yet been processed, but if you preorder we’ll process it faster
and notify you when it’s ready.
Right.