[2bitlobster]

Don’t Make Me Think, by Steve Krug. I used it for years as a required text in pretty much every UX related class I taught. Entertaining, super digestable and very nutritious.

[karaterobot]

I expected to see this one or "The Design of Everyday Things" by Don Norman. I don't know a designer who hasn't read one or both.

[kriro]

It taught me to smile whenever I see a door or use a faucet. One of the great gems that I picked up on a complete whim.

This "Don't Make me Think" which the parent suggested and "About Face: The Essentials of Interaction Design" are my "UXy" books on the shelve.

[carlmr]

I'm not a designer, but I found TDoET immensely helpful in terms of designing software interfaces, be it APIs or GUIs.

It really teaches a few simple concepts that apply in wide ranging areas.