Google’s ebookstore lets you buy and read ebooks virtually on any device you want. The service stores your purchases on the cloud (as opposed to downloading locally on your device), so you have access to millions of book anywhere. Your reading status is synced to all the devices, so, say if you were on page 153 of a book when you were reading it on your iPad, you can continue from the same page when you open it up on your iPhone.
You can read the ebooks in the web based reader or on apps available for Android, iOS, nook & Sony ebook readers. These apps support offline reading. The apps are pretty basic in nature as compared to the native apps on these devices. Although, the iOS app does have the crappy flip animation when you turn the page.
Note that the service is not yet available for the Amazon Kindle.
Here is how a typical book looks in the web based reader:
And here is a short video demonstrating the service:
[via Google Operating System]