Inkling is now going to get the chance to be the first to grab the attention of students at over 900 colleges. Students aren't buying as many textbooks as they used to, but when they do buy they generally start from the bookstore website. Now they will see Inkling's logo while browsing, and that means they will be more likely to buy their textbooks via Inkling. Of course, Inkling doesn't offer much in the way of selection yet, so this might not help boost their sales.
Again, that's not that big of a deal, but consider what it might mean with respect to the rest of the market. For example, Kno doesn't have any bookstore deals like this so they are at something of a disadvantage. Newco, B&N's new spinoff, is set to dominate the 600+ bookstores that B&N college now operates. I don't know yet what Newco will be doing with respect to digital textbooks, but chances are that ti will be disruptive of paper textbook sales and thus increase the sale of digital textbooks via Newco.
Newco's 600 stores is what makes Inkling's announcement today such a big deal. The campus bookstore no longer has the schoolwide exclusivity that it used to, but it is still at the core of student's textbook buying. Inkling is now going to be at that core experience in nearly a thousand college bookstores supplying nearly 5 million students. That might give them an advantage over the digital textbook platforms that don't have the same level of access.
This might be an stretch, but I think we are going to see a format war break out in the digital textbook market. Inkling just made themselves (at the very least) a stronger player in that fight.
P.S. I don't think Inkling's format will win; it's too cost intensive and outside the reach of the independent author. But it is one of the majors now.