The author comes across as arrogant and condescending most of the time. I'd recommend skipping Parts I and II altogether, where she brags about herself then lays down all sorts of "musts" if you want to be a "real" writer. Writers have an amazing talent for procrastinating: I must clean the entire house-, I must paint the bedroom-, I must find a new job before I can start writing. Brown's "Must study Latin first" rule discussed by others above strikes me as a colossal example for this. I'm sure studying Latin is one of many effective ways to improve your craft, but to insist writers should not even put pen to paper until those two years of study are complete seems the height of lunacy.
Authors interested in writing mystery, fantasy, horror, SF, etc, will likely be put off by her repeated declaration that genre fiction is on the far edges of the distant suburbs of fiction, and none of her rules apply to it because it isn't real writing.
Part IV - a whip around of the peculiarities of writing different forms and in different media (television and film scripts, magazine articles, plays, etc - is of minor interest, short stories are blown off altogether.
Part V, her curriculum for a writers conservatory, would be better shared with an academic journal.
Part VI, her 30+ page reading list of critical works of fiction through the ages, starting in 665 AD, feels like it's pulled from a doctoral dissertation.
It's an interesting list, and contains many excellent works of genre:
The Murders in the Rue Morgue: The Dupin Tales (Modern Library Classics),
The Complete Adventures and Memoirs of Sherlock Holmes,
Dracula (Signet Classics), the poems of
Edgar Allan Poe: Complete Tales & Poems,
Alice's Adventures in Wonderland and Through the Looking-Glass (Modern Library Classics),
Riders of the Purple Sage (Leisure Historical Fiction),
Tarzan of the Apes_, Agatha Christie's
Mysterious Affair at Styles: A Hercule Poirot Mystery,
The Thin Man, and many others, rather belies her claim that genre fiction isn't worthy of anyone's time. Reading it in chronological order, as she insists must be done, would likely show some interesting developments in the field over time, but again, that strikes me as a doctoral dissertation requirement. There is value in reading some or all of these books, in whatever order the reader prefers.
If I were to recommend this book to anyone, it would be for Part III: The Work, where Brown focuses on language. There is much that is interesting here, especially the section where she explores vocabulary and the difference in intent and power between synonyms that derived from Old English/Anglo-Saxon (more powerful, language of the common people) versus Latin/French (more formal, language of the rulers and rich).
For example: woman vs female, lonely vs solitary, help vs aid, feed vs nourish.
The section on verbs, and the power of the passive voice when used *appropriately* was quite interesting.