I am writing an application where I need to find the google volume id from ISBN. When I query google books API with query https://books.googleapis.com/books/v1/volumes?q=isbn: in many cases it works fine. But I have a bunch of books where I have the following (for example 9782070370016). For the query https://books.googleapis.com/books/v1/volumes?q=isbn:9782070370016 it replies that this book is unknown. OK, it might not be in Google data base...
But when I query the french site https://books.google.fr/books?vid=ISBN9782070370016 it replies that this book does indeed exists and the Google volume id is lwb2zwEACAAJ and it is an edition of Germinal by Emile Zola
So why is it that it fails when I query Google Books API though this volume is known from Google? I did not find a way to contact Google directly...