Before the iPhone, back in 2003 I had a problem. I love to read books. I hang out at book stores like some people hang out at bars. Back then I would buy books on impulse. I would be riding high on the thrill of a new book once I left the book store. But the high was short lived.

Immediately after purchasing the book, I’d think, “I bet this is cheaper on Amazon.” How much could I have saved if I had waited and purchased the book on Amazon? 10 cents? 10 dollars? But then I would have to wait for it to be delivered.

This slideshow requires JavaScript.

To buy or not to buy

The only way of weighing the options and deciding if I should buy the book there at the book store or wait and purchase it on Amazon was to find out the price of the book on Amazon while I was at the store. The only thing worse than finding the price difference was nominal after buying the book would be to not have the book once I got home and find out that the price difference was minimal. But this was 2003, web browsers couldn’t handle full web pages. I decided to take action.

I signed up for access to the Amazon RESTful API by becoming an Amazon Associate. In about a month I had written a web service that did the job for me. I created a simple site at that functioned like a google for books. Type in the ISBN found on the back of the book and in less than a second you would have the price, the ratings, and the reviews of that book. Once I launched the service it was featured on LifeHacker and some revenue from the 4% referral fees started to trickle in.

Changes in the API

Not only was I able to pull up real time prices and reviews, I was making enough money with ISBNspy I could buy my books with the referral fees. A few years ago Amazon revised their API and restricted ratings and reviews. lost a lot of the customers that were using the site on a regular basis. I decided to retire the site and focus on native iPhone programming and created Mathogen.

Check out my other Projects: