The mission statement of Companion guide is to facilitate the demystification of a difficult subject and to convey some of the excitement and wonder of a revolution with no end in sight. If you are presently studying semiconductor devices search for those areas you feel somewhat unsure about and try to connect to my explanation. You may find that my "take" is somewhat non- conventional which hopefully will add another perspective. In the event that you find my explanation confusing rather than clarifying please let me know; I'll attempt to modify, correct, or perhaps completely overhaul my reasoning and together we can come to a better approach. One reason that the text is so long is that nearly all relevant equations are derived in detail hopefully relieving you of the burden, sometimes quite frustrating, of deriving them independently. I would especially recommend going over the solved problems as they were chosen from a relatively larger set to illustrate and clarify the subject matter. If you have previously studied the material and are interested in refreshing your understanding I would suggest skimming thru the first two chapters and starting with chapter 3. There is really little need in your situation to go thru the detailed derivations of each equation; rather your time is probably better spent focusing on the discussions and problem solutions. Skim thru those areas which perhaps are more familiar, concentrating of those subjects which caused the most confusion.If you have not studied this material at all or perhaps are planning to take a semiconductor course in the future you may be able to benefit from a brief overview of the subject matter. Read thru the first few chapters especially chapter 3; focus on the introductions, chapter summaries and the discussion sections. Pay little, if any, attention to the equation derivations but try to understand at least one or two examples from each chapter and the worked problem chapters. Understand the semiconductor structure tree and how each device configuration is built from more basic structures. Finally, If you presently teach a course in semiconductor devices and find some of my explanations intriguing as well as controversial lets see if together we can find innovative ways to present this rather difficult and exciting material