This is not a comprehensive list -- there are many other books worth buying. Here we mention just a few user interface books that don't gather dust on our shelves.
C++ GUI Programming with Qt 4, Second Edition by Jasmin Blanchette and Mark Summerfield, ISBN 0-13-235416-0. This is the official Qt book written by two veteran Trolls. The first edition, which is based on Qt 4.1, is available online. The second edition, based on Qt 4.3, is also available online.
The Design of Everyday Things by Donald Norman, ISBN 0-38526774-6, is one of the classics of human interface design. Norman shows how badly something as simple as a kitchen stove can be designed, and everyone should read it who will design a dialog box, write an error message, or design just about anything else humans are supposed to use.
GUI Design Handbook by Susan Fowler, ISBN 0-07-059274-8, is an alphabetical dictionary of widgets and other user interface elements, with comprehensive coverage of each. Each chapter covers one widget or other element, contains the most important recommendation from the Macintosh, Windows and Motif style guides, notes about common problems, comparison with other widgets that can serve some of the same roles as this one, etc.
Design Patterns - Elements of Reusable Object-Oriented Software by Gamma, Helm, Johnson, and Vlissides, ISBN 0-201-63361-2, provides more information on the Model-View-Controller (MVC) paradigm, explaining MVC and its sub-patterns in detail.
Macintosh Human Interface Guidelines, Second Edition, ISBN 0-201-62216-5, is worth buying for the don'ts alone. Even if you're not writing Macintosh software, avoiding most of what it advises against will produce more easily comprehensible software. Doing what it tells you to do may also help. This book is now available online and there is a Mac OS 8 addendum.
The Microsoft Windows User Experience, ISBN 1-55615-679-0, is Microsoft's look and feel bible. Indispensable for everyone who has customers that worship Microsoft, and it's quite good, too.
The Icon Book by William Horton, ISBN 0-471-59900-X, is perhaps the only thorough coverage of icons and icon use in software. In order for icons to be successful, people must be able to do four things with them: decode, recognize, find and activate them. This book explains these goals from scratch and how to reach them, both with single icons and icon families. Some 500 examples are scattered throughout the text.
These books are made available in association with Amazon.com, our favorite online bookstore. Here is more information about Amazon.com's shipping options and its customer service. When you buy a book by following one of these links, Amazon.com gives about 15% of the purchase price to Amnesty International.