I'm not always getting results when searching by isbn with the Google Books API
For example, this ISBN won't work with the ISBN query
https://www.googleapis.com/books/v1/volumes?q=isbn:9780593437810&maxResults=40&langRestrict=en
but if I remove it like so:
https://www.googleapis.com/books/v1/volumes?q=9780593437810&maxResults=40&langRestrict=en
then it brings up a bunch of results but I'm trying to narrow it down to only one. The isbn query works on some books and not others