Of all the rumors swirling around the Apple Tablet expected to be announced on Wednesday, the one most everyone can agree on is that it will be used as a full color electronic reader which will put Amazon’s Kindle to shame. Over the past few weeks, Apple has been negotiating a flurry of last-minute deals directly with book publishers such as HarperCollins and McGraw-Hill.  Magazine and newspaper publishers are salivating to get on the device.  But one unanswered question so far is whether Apple will add books and magazines to iTunes or create an entirely new e-book store from scratch.

We believe there is a good chance there will be a Barnes & Noble bookstore built into the Apple Tablet, either as one of the showcase apps which launches with the device, powering a new book section in iTunes, or integrated directly into the Tablet’s e-reader. The two companies are thought to be working closely together, increasing the likelihood that Barnes & Noble will be part of the announcement on Wednesday. While Apple can run around cutting deals with the larger publishers, a built-in Barnes & Noble bookstore could include up to a million titles in one fell swoop, just like on B&N’s own Nook reader. Barnes & Noble already offers an eReader app for the iPhone (iTunes link) which lets you download and read electronic books on the smaller device. That app could be paving the way for an eReader or book store on the Tablet.

Of course, Amazon also has a Kindle app for the iPhone which allows people to buy electronic books from its store. We don’t know whether Apple is also working with Amazon for Wednesday’s launch, although given the recent moves by Amazon to shore up the Kindle in anticipation of Apple’s technicolor onslaught seeing them on stage would be really surprising.  Allowing Amazon to create a Kindle app for the Tablet, though, seems more reasonable.  After all, Apple wants to sell Tablets.  If it doesn’t have to get into the bookstore business to do that, why should it?

For Barnes & Noble, however, if it can manage to become the default bookstore on the Tablet, or simply squeeze its app into a preferred slot, it could make real inroads against the Kindle. An Apple Tablet tied to a Barnes & Noble digital bookstore must be Jeff Bezos’ worst nightmare.