Did Apple eject Google Books from the App Store for violating terms?

For reasons yet undefined, Google Books has been removed from the iTunes App Store.  We noticed the App was gone earlier this week but thought it might have been just a blip.  Now it has been awhile.

Google Books was just updated in April with new 3D page turning, landscape mode and search so it is unlikely that Google decided to orphan it.  Google launched its Books initiative in December of this year as a competitor to Amazon and Apple’s eBookstores.

So why is it gone now?  The timing with Apple’s new, controversial Terms of Service would seem like the most obvious explanation.

Was Google in violation of Apple’s new in-app purchase terms of service? Or, is this because Harry Potter is coming out on Google Books?

We’ve reached out to Google and Apple for answers.