why is default setting for google 'books' so tiny

Why don't you just use the Google Play Books App on your iPad?

https://itunes.apple.com/us/app/google-play-books/id400989007

that is how the site looks on my desktop too (but of cause the screen being 27" makes that less of a problem), so the issue is that google does not have a mobile friendly version to send the tablet browser to

Wow. What a snippy response. You do know we are just volunteer's here helping other users. You were having an issue with the web version. I simply suggested using the App. Since you can't adjust what the web browser provides (Fact - Not Opinion), I'd recommend you reach out to Google, as Apple has no control over anything Google puts out through a web browser.

And you're welcome.

I wasn't being snippy. The fact is, you can't change how Google renders their page on a browser. So if that's how you wish to use the service, you'll have to live with it. We can't change it for you. Apple can't change it for you.

But good luck to you and do let us know if you get Google to change it for you.

Clearly your choice, but then you'll just have to live with how Google renders on the browser. The App is fully optimized specifically for the iPad screen.