Update: Good news! Jaroslav Toulash emailed me that he published a book on Practical API Design !!!
Looks like Brian McAllister may be preparing a talk on Designing Elegant APIs.
I've been very interested in good API design for a long time. But I could never find a single book on the subject. Many design and programming books provide good advice and guidelines that are essential for designing good APIs, but none of them tackles the matter directly.
I reviewed "Interface Oriented Programming" a few months back with disappointment. It may not be a bad book, but I felt it was quite basic and superficial. May be my expectations were too high, and too focused on API design.
Over time, I collected some links on the subject and shared some with Brian:
API: Design Matters - Article by Michi Henning, ZeroC, for ACM Queue magazine.
Interface Design, Best Practices in Object-Oriented API Design in Java, by Bill Venners - This one is a Book in progress!. Unfortunately, the last updates seem to be from 2002 or so. I'm not sure if the project is still alive. Anyway, it contains many good articles.
How To Design a (module) API - A great page on good design practices for writing APIs. It's tailored for NetBeans module writers, but is still pretty general and gives very valuable guidelines.
How to Write APIs That Will Stand the Test of Time - A session I attended at JavaOne 2006. Presented by Tim Boudreau and Jaroslav Tulach, members of the NetBeans team. It focuses on API evolution and compatibility, but also covers usability and other guidelines. I guess they are the main guys behind NetBeans' How To Design a (module) API page linked above.
I had the chance to speak with Jaroslav after his session and suggested he should write a book on this topic. I emailed him the references I had, and he said he would try to draft something by the end of year.
API Usability - Focused on making APIs easy to use. The article applies general usability principles (commonly used in GUI design) to the design of APIs.
Measuring API Usability - An interesting article by a usability engineer at Microsoft, published on Dr. Dobb's. It favors the use of scenario-based design to achieve usable APIs, and explains the use of their "cognitive dimensions" framework for measuring API usability. He also blogs about API usability.
Java API Design Guidelines - A good article from a developer who was also surprised by the lack of a book about API design. He collected some advice and additional links.
XOM Design Principles - Some design "principles" followed by XOM (an XML parsing library).
The Most Important Design Guideline? - A short article by C++ guru Scott Meyers.
Humane Interface, Minimal Interface, Designed Inheritance, DSL Boundary, Duck Interface, Fluent Interface, Public vs. Published Interfaces - Some of the many great writings from Martin Fowler. These selection is on specific topics that are relevant to API design. Most of them are quite recent.
Programmers are People, Too - An article by Ken Arnold for ACM Queue magazine: "Programming language and API designers can learn a lot from the field of human-factors design."
So, let's hope Brian gives his talk at a big conference, signs a contract with a big publisher and fills the void.