The sweets are not only useful models, they also indicate the desire of the authors to make this a readable and entertaining book as well as a very serious attempt to advance our theoretical understanding of this complex and confusing topic.
The Dahms have been developing and advancing a new theory for the last few years. This book brings it together. It explains the nature of reflected radiation and then the problem of finding a mathematical description of it. In their quest, they have rediscovered and used mathematics that was invented by Sir George Strokes in the 1860s!
Much of the current use of near infrared spectroscopy utilizes diffuse reflection or transmission. According to Karl Norris "The development of NIR analysis is being restricted by our lack of a theoretical understanding of diffuse reflection" and he should know!