I like the idea and honestly I'm surprised there are that many arbitrage opportunities that aren't already taken advantage of. I guess you're hoping to outsource the cost of shipping, storage, etc. while still getting some money for finding the deal.

But if you don't want to go through the hassle of buying and selling the book yourself for that amount of profit, what makes you think other people will? Why not just make all these deals yourself and take 100% of the profit?

Edit: I guess you answer my question in the FAQ. I'm just not sure I believe you're making this service because you are "nice like that". Not that I'm against what you made; I actually think it's really cool. I just genuinely think you would able to make a lot more money for less work than you think if you scaled up the buying and selling yourself. I think it would scale, quite well in fact.