Don't Make Me Think, A Common Sense to Web Usability, by Steve Krug.

This is the book that describes what people are really thinking when they browse websites. Often, we place significant amount of time designing the aesthetics and expect that people will use the website according to how its designed. This book exposes the reality of how people really look at a website's elements. The topics are presented with helpful visuals that clearly illustrate main points of the web usability.

This is definitely not a book that tells about some cognitive psychology facts that detail all aspect of how human beings interpret things. This doesn't present deep science, but rather gives a lighter, common sense approach as to why is there a need to understand the factors that could drive people away from the website.