I was working on a review for another textbook app today, and I decided to try Inkling so I could compare the 2. (Plus Inkling had been updated this week, so now was as good of a time as any.) I never really got far into the app because I don't think it's worth the time and effort. It has a number of really cool features, but it just doesn't have the selection.
One of my first steps was to check out the in-app ebookstore and see how many titles were offered. There's only 25 ebooks available for this platform, and that's out of the tens of thousands of textbooks available. That's going to be a killer.
It would be one thing for a company to have only 25 fiction titles available. A company could do quite well on that, so long as their work was good and they went for familiar stories. If the story is the same then it doesn't really matter where you buy it.
A textbook app, on the other hand, needs to have (nearly) everything. Students don't just need a chemistry textbook; they need a specific chemistry textbook. And without students buying textbooks, there's no income.
It's been just over 8 months since this app was launched, and it's adding content at a glacial pace. If this is all that Inkling plan to do then they won't survive.
But I bet they'll come up with a new business model. (Or someone will buy the remains, and then figure out a better idea.)