How to get the extra large cover image from google book API?

Question

According to Google doc, using this link can get the URL extra large for a book

Google doc

However, when I clicked https://www.googleapis.com/books/v1/volumes/zyTCAlFPjgYC , there are only 2 thumbnails (small and medium). So do I need to obtain a Google API key to get full information about a book ?

Answer 1

I figured out that you can replace the &zoom=1 part of the URL with &zoom=0 for larger images, but only in some cases.

For an example, this is the Sherlock Holmes small thumbnail:

http://bks5.books.google.com/books?id=buc0AAAAMAAJ&printsec=frontcover&img=1&zoom=1&edge=curl&source=gbs_api

Now, by setting zoom to 0, I get a large thumbnail:

http://bks5.books.google.com/books?id=buc0AAAAMAAJ&printsec=frontcover&img=1&zoom=0&edge=curl&source=gbs_api

Answer 2

Actually with some books, google provides large image but some not.