People ask me, "I want to learn about usability, where do I start?" There are some excellent introductory books on the subject.
Donald Norman's sharp, incisive book The Design of Everyday Things first turned me on to usability. Norman's examples are accessible to anyone, and his book is full of powerful, commonsense advice that stuck with me from the first reading. One of my favorite lines is (paraphrasing), "A door should not need an instruction manual to use -- even if the manual is one word long."
My favorite basics book specific to the usability field is Steve Krug's Don't Make Me Think. Again, Krug is full of practical, real-world guidance that just makes sense.