I've owned this book for about 3 years and have used it a lot as I get more into my biking and bike maintenance. It recently struck me that this book is not actually all that great! It does have some great exploded diagrams that have been very useful for working on wheel bearings and gears. Beyond this though the book is very average and other books I've scanned through, such as the Haynes bike manual, look much better in my opinion.
Perhaps my biggest criticism is the amount of words Mr Zinn uses, simply an unnecessary volume. This book is huge and the majority of it is words for the sake of words and not technical guidance.
I loved it to begin with but less of a fan as I've gotten more experience.