"I had to actually purchase a book to learn the API and write the client. It was pretty frustrating trying to learn the API and develop a product quickly"

In this quote, Shawn Fanning is expressing his frustration with needing to buy a book in order to learn the API (Application Programming Interface) and compose a customer. The API is a set of protocols and tools that allow different software applications to interact with each other. Fanning's use of the word "really" recommends that he was surprised or disappointed that he needed to spend cash to learn this details. He then goes on to explain the problem of learning the API and establishing a product rapidly, indicating that it was a tough and time-consuming process. This quote highlights the importance of having available and easy to use resources for designers to learn and utilize APIs efficiently.