Concept Testing by David Schwartz (1987, Hardcover)

I am a market researcher for one of the largest global CPG companies in the world and I was told from coworkers that this is the concept testing "Bible" for our advanced analytics researchers. The researchers who know what they are doing all seem to have a copy. If you are inclined to buy it too, it is a good idea to buy when you can because it is out of print. It is definitely dated (my copy was printed almost 20 years ago), but the theory behind the designs and the cautions all still apply, even if the examples seem simple today. It was very easy for me to follow and I picked up several new techniques, even though I have been doing concept tests on the supply and client side for three years.