Note that the list might be outdated - they mentioned GoodRead's API which is deprecated (they no longer accept new developers to signup). I know this because I was recently researching on creating a book recommendation hobby project.
Goodread API are not maintained or as tou mentioned depreciated.
Like you I was also working on side project to fetch bookquotes along with source author/book.
Finally, I had to use web scrapping to make application work.