This book is based on lecture notes left behind by the late Durham professor Archie Barnes. This is obvious not only from the preface, but also from the messy nature of the book itself. This is a chaotic attempt at writing a cohesive grammar of Classical Chinese. The section on the infamous "empty words" (虛詞) is placed at the back of the book, most of which is filled with an awkward attempt to explain the grammar of Classical Chinese in terms more familiar to Western students.
The biggest problem that Barnes and his posthumous editors encounter is having to introduce difficult characters and concepts right from the start. After a brief introduction to nouns, the reader is exposed directly to full sentences with little additional commentary or assistance - causing me to wonder whether this was actually intended for beginning learners or more advanced students. This is a problem common with English language Classical Chinese learning material; perhaps the true problem is that the best method is to simply dive into the wealth of extant material and try to float.
Barnes makes no distinction between common and uncommon ways to say the same thing, other than a few occasional parenthetical references here and there. For example, after finishing this book, an inexperienced reader would not know whether 乎, 與, 歟,耶, 邪, or 諸 is the most common interrogative, and is likely to face extreme trouble in determining which of the myriad uses of 則 or 之 she is encountering in any given text. These notes simply lay down the rule and give a few token examples here and there without really broaching the underlying grammatical ideas.
That's not to say that this is all bad. The examples used are colorful and interesting, citing long enough excerpts to help the reader understand the grammar in context while keeping things short enough to be Anki-friendly. The grammar here is quite comprehensive, so long as the reader is prepared to fish around a bit and grab pieces of the puzzle here and there. The translations are also concise, simple, and lack inappropriate sexual commentary (as opposed to, say, Paul Rouzer's textbook).
My biggest question here is precisely whom this handbook was designed for. A beginner will find this simply overwhelming, even with the glossary included at the end. An advanced learner will find this far too simple and too unorganized to be of any practical use. Intermediate students of the language would get more mileage from interacting directly with original texts.
I would love to see a comprehensive treatment of Classical Chinese grammar similar to the Routledge series of comprehensive grammars of modern languages. Perhaps one day we will have a text that analyzes Classical Chinese on its own terms, rather than arbitrarily stuffing it into a Western language mold. Until that day comes, Du's grammar is at least an adequate start.