Keep Coding

I am little bit confused interpreting the Google Book API terms. In this page it is written that
Note: Performing a search does not require authentication, so you do
not have to provide the Authorization HTTP header with the GET
request. However, if the call is made with authentication, each Volume
will include user-specific information, such as purchased status.
Does that mean I don't need to use an API key for searching book info or linking cover from google books (to be used in Android App)?
Thanks

For searching only the informations about books (author, title, etc..) you can write code without have any API key. But probably for the payment service or other (write a book and insert that in google book api) you should have an API Key (with sign up).
Bye bye