For "Usability Testing", I would recommend Steve Krug's second book, "It's Not Rocket Surgery", rather than "Don’t Make Me Think". "It's Not Rocket Surgery" is

For "Usability Testing", I would recommend Steve Krug's second book, "It's Not Rocket Surgery", rather than "Don’t Make Me Think". "It's Not Rocket Surgery" is entirely about usability testing, whereas his first book only dedicates 1-2 chapters to it.