Use Books API on Google Apps Scripts !? No! No!

It apperars the Google guys don’t like us to use some APIs directly in their Google Apps Scripts platform. I don’t see  the Books API in the list of libraries available from the top menu and also when I try to access it directly using the UrlFetchApp predefined object it salutes me with a “403 Forbidden” or “404 Not found”. What’s the problem Google guys ? Since this particular API it’s free and does not requires authentication are you afraid of someone can abuse it !? I just wanna use it for the purpose of getting the ISBN of some books automatically, but you Google guys are afraid I’m going to abuse it like some people on the past used the Translation API !?