Understanding the NEC Volume 1 was written to provide insight into, and an understanding of, many of the technical rules of the NEC. This book, printed in four colors, contains clear graphics, examples.
Mike holt is a master at taking the complex and putting it into simple, practical terms that can be understood by the electrician in the field. I am currently studying for my master electrician's exam and I find his publications very helpful.
This book explains the first four chapters of the National Electrical Code in great detail. It doesn't cover every single rule, but covers most. The graphics are outstanding in their detail, clarity and accuracy...as they say 'a picture is worth a thousand words' and the National Electrical Code has no pictures and thousands of words. So his illustrations help in a great way.
A word of caution: for someone trying to learn the electrical trade, this is not the place to start. You need to understand theory and have some basic electrical experience before you can grasp some of the concepts in this book.
Overall, great for the electrician who really wants to learn the meaning of the code rules and how to apply them.