Even if you are going to purchase book on a subject, this finds so much stuff that is not in Google because of copyright delisting and is sometimes useful in knowing which books to consider.
Yandex results especially the non English ones can be good if you are willing to use a translator.
Some libgen clone sites like z-lib have fulltext search on books with support for exact matches: https://zlibrary-asia.se/fulltext/?q=%22frank+sinatra%22&typ...
Even if you are going to purchase book on a subject, this finds so much stuff that is not in Google because of copyright delisting and is sometimes useful in knowing which books to consider.
Yandex results especially the non English ones can be good if you are willing to use a translator.