wow out of all the comments only one person actually answered the question
https://booksliced.com/books/the-exact-ebook-market-shares-o...
The Goodreads integration into Kindle cannot be overstated.
But, you just have to approach it from different angles. Don't attempt to compete with Goodreads, but rather build something better that works in a new way around people's desires around books.
Goodreads is just a review database, easy to innovate around that barrier.