We expected Google to launch its upcoming e-book store before the end of the year, and the company announced Monday that the new Google eBookstore is now open for business in the US. Google is touting the "open" nature of its e-books by making them accessible to the widest array of popular e-reader devices, including the iPad, Nook, and Sony Reader.

Google's new eBookstore works a little differently than other stores—at least when it comes to reading via computer. All purchased titles are kept in Google's cloud-based storage and accessed via a browser. When reading via an iOS or Android-based device, a dedicated app can download and cache titles for reading offline. And for devices compatible with Adobe's DRM-protected e-book formats—including Sony Reader and Barnes & Noble Nook—PDF or EPUB files can be downloaded and transferred to your device using Adobe Editions software.

Those hoping Google meant "DRM-free" when it said "open" will be disappointed, though, as may users of Amazon's popular Kindle e-reader. "Currently, Google eBooks are not compatible with Amazon Kindle devices, though we are open to supporting them in the future," the company noted in a support document.

Google has also partnered with Powell's, Alibris, and participating members of the American Booksellers Association to offer rebranded Google e-books through their respective websites. "You can choose where to buy your e-books like you choose where to buy your print books, and keep them all on the same bookshelf regardless of where you got them," according to Google Books product manager Abraham Murray.

Google said that its library of over 3 million books is one of the largest in the world. "Hundreds of thousands" are on sale (similar to libraries from Amazon, Kobo, and Apple) while the rest are public domain titles available from the Google Books project.

The proposed settlement to sell e-book versions of copyrighted books hasn't yet received final approval from the courts, but the Google eBookstore puts all the technological pieces in to place so additional titles can be made available once it is. Some publishers worried that approval of the deal could create an e-book duopoly between Amazon and Google, but Apple's iBookstore and Barnes & Noble's Kobo-powered store have opened since it was originally announced.