Barnes & Noble is set to take on Amazon and Apple with two new versions of its Nook tablet unveiled today, joining an already crowded marketplace.

The new devices are a Nook HD tablet with a 7-inch screen, starting at $199, and a Nook HD+ with a new 9-inch screen, starting at $269.

In addition to new HD screens and a lighter body, Barnes & Noble is also increasing the services the Nook offers, adding a video purchase and rental service, allowing users to maintain different “profiles” and making it easier to browse titles in its book and magazine stores.

New York-based Barnes & Noble, the largest traditional U.S. bookseller, has invested heavily in its Nook e-reader and e-books.

Barnes and Noble CEO William Lynch unveils the new NOOK HD plus, left, and NOOK HD in New York

Barnes & Noble will continue to sell its smaller black-and-white e-reader, called the Nook Simple Touch, for $99, and a backlit Nook Simple Touch for $139.

The Nook HD runs on Google’s Android 4.0 system and includes Barnes & Noble’s own app store and browser. It is an upgrade to the hardware and services offered by its previous tablets, the Nook Tablet and Nook Color, which Barnes & Noble is phasing out.

However, Barnes & Noble faces a tough battle.

Seven out of every 10 tablets sold in the second quarter were iPads, according to IHS iSuppli.

Amazon.com has a 4.2% share of the tablet market, while Barnes & Noble has a 1.9%, according to iSuppli.

However, experts say the bookseller is in with a chance.

“If the decision the consumer is making is whether to buy based on hardware, these new Nooks will beat out Amazon,” said Forrester analyst James McQuivey.

“But that’s not the decision every consumer is going to make – hardware is only as good as the services the hardware enables.”

So far, Amazon offers more services, James McQuivey said, with a bigger app store, and more extensive video library, not to mention Amazon’s vast product offerings and its Amazon Prime free-shipping service.

In an attempt to measure up, Barnes & Noble is launching a video service that lets users buy and watch movies and TV shows on their mobile devices and televisions.

The offerings will come from major studios including HBO, Sony Pictures, Viacom and Warner Brothers. Scrapbook and catalog browsing features have also been added.

One wild card working in Barnes & Noble’s favor this holiday: Wal-Mart and Target, increasingly threatened by Amazon’s online retail operations, won’t carry the Kindle. The retailers will sell Barnes & Noble’s Nooks, as well as other tablets like the iPad.

“This is going to be a lot of fun to watch over the next year,” James McQuivey said.

The new Nooks are available for pre-order online and in stores beginning on Wednesday and will begin shipping in late October and begin arriving in stores in early November.

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