Joel's: User Interface Design for Programmers
Well, I've finally finished reading it. I've got to say it has opened my eyes to UI design. I've been involved din the UI Design of Consoles and Intranet Applications for nearly 10 years now. And must of it was common sense but others where like a light switches being turned on.
The books is only 134 Pages long and is in quite large print so it a fairly short book and yes you can read it online but as Joel says "but it's longer, with about 50% all-new material that isn't available online."
I think from now on it will make me thing more from the dumb user point of view rather then a programming that can use the computer and mouse. Not saying that all users are dumb but if you can work for the lowest common denominator you've got more chance to succeed.
The only issue I have is with Chapter 17 about using FLASH on a website I think now we have Flash 7/8 and Flex it doesn't limit the users as much as it probably did back when the book was written in 2001. With flash now on 97.3% of desktops flash isn't a hindrance any more and if you don't have it, it's only around 1000K download for PC/MAC and with Broadband how long does that take? Even on a 56k Modem Adobe's website says it should only take 2 minutes, in the big scheme of things tha's no time at all.
I truly recommend this book for every developer out that involved in the anyway with User Interfaces be it design/implementation it really makes you think about it.

