Is this the end of Amazon’s ebook reign? Google is launching its new open ebook store today, simply called Google eBooks, with over 3 million titles, in a bid to take on the ebook world dominated by Amazon, Barnes and Noble, and Apple.

As we reported previously, Google’s ebook venture will be more open than its competition. Consumers will be able to browse and search Google’s enormous ebook library, and they can read ebooks on any web enabled device. Your ebook library will be tied to your Google account and will be accessible through any web browser. You’ll be able to buy ebooks directly from Google, or from independent bookseller partners like Powell’s, Alibris and participating members of the American Bookseller’s Association.

Google wisely isn’t relying on the web entirely, as the company is releasing free Google eBooks apps for the iPhone, iPad, and Android devices. The apps will let users continue reading where they left off when they switch devices, just like ebook reading apps from Amazon and Apple. You’ll also be able to browse and purchase ebooks from within the apps. Google is also providing an app for Barnes and Noble’s Nook and Sony’s ebook readers. There’s no word on Kindle compatibility yet, but I wouldn’t hold your breath for that.

The ebook store will also tie into Google Books, the company’s digitization project for the world’s books. Google says that is has scanned more than 15 million books since the project began in 2004 from more than 35,000 publishers. You’ll be able to search through Google’s scanned offerings in the research section of its ebook store.

I don’t suspect that Google will initially be very successful with this ebook venture. Competitors like Amazon and Barnes and Noble are already entrenched in the market, and consumers interested in ebooks are already loyal to at least one of Google’s competitors. But Google does boast a bigger library than the rest with 3 million titles (including some 2 million free public domain titles), compared to Barnes and Noble’s 2 million (with public domain titles) and Amazon’s 750,000 (not including public domain). It’s unclear how Google’s paid ebook library compares to Amazon’s, a company that has had years to form relationships with publishers.

The open nature of Google’s ebook store may eventually help the company grab a bigger slice of the market. You’ll eventually be able to purchase Google ebooks from multiple sources, as well as see them marketed on blogs and other sites on the web. That’s a big difference from Amazon’s Kindle books, which you can only purchase from within Amazon’s store. Google also has the advantage of not being burdened by a device — instead it’s built a system that can work with practically any device.