Your competition is something like getabstract.com & summary.com (you can find a bunch by typing in “cliffnotes for business books” in google).

I think you can learn a lot from seeing their sites (none are gorgeous). I’d also consider PPC to acquire customers, but perhaps you could have an alternative pricing model (per book, per month, per year, audio versions of the summaries.)

You could always offer a handful of “life-time accounts” to try and bump the short-term revenue enough that you can flesh out your library more (I feel like that might be a limiting factor for customer acquisition).

Feel free to reach out to me on twitter if you’d like to continue the conversation @ckluis.