For writers, About Writing is a drop-everything-and-read-right-now kind of book that can be used while you're going over your outline, while you're writing a scene or a chapter, and while you're revising that scene or chapter. This is not the kind of book you'll want to wait until the end of writing to read, rather you should consider using About Writing as a reference during the process. For teachers, his Introduction, essays, and appendix could be useful tools in an intermediate to advanced fiction writing course--although not as hand outs but as points of discussion.
Do not skip the Preface or the Introduction, as both are packed with ideas on good writing versus talented writing, which will make you study each paragraph of your writing for clarity and language. Of his essays, "Some Notes for the Intermediate and Advanced Creative Writing Student" is the most inspired and inspiring. This essay is on narrative structure, but more than that, it is about breaking away from the formulaic narrative structures that can hold a novel to mediocre writing. He advocates knowing the old structure in order to revise or subvert it. He makes a point of differentiating plot and structure: "Plot exists as a synopsis that often has no correspondence to text.... Structure exists, however, only in terms of a particular text, so that to talk about it in any specificity or detail you must constantly be pointing to one part of a page or another, at these words or at those: structure is specifically the organization of various and varied textual units." (p. 144)
Of his letters, read Letter to Q--. It is a criticism of Toni Morrison's Bluest Eye, from the intention of the writer to the failure of the historical milieu to the biased discussion on intra-racial discrimination. It's a brilliant rant: "I begrudge no one his or her enjoyment of Morrison's novel. Still, I feel obliged to say: If a reader thinks this story gives an accurate or even a meaningful portrait either of the subjective lives of dark-skinned black or of light-skinned blacks, that reader knows none of us. And that goes for black readers as well as white." (p. 176)
His interviews were included because he sees them as a form of written work, because he received the questions in writing and answered them in writing. This section could have been strengthened with the interview, "Black to the Future," which discusses William Gibson's critically acclaimed and popular Cyberpunk novel, Neuromancer.
About Writing ends with an appendix on various topics, from POV to punctuation to a discussion of the axiom: write what you know. If you only read the appendix, you'd still be better off now that where you were as a writer before.
The primary strength of About Writing is the many ways Delany discusses writing from the point of view of writer, reader, a teacher, and a critic.
The primary weakness is that the package deal of Delany's experience, success, and knowledge comes with a tone that can be off-putting, a tone supported by his edict in the Preface that only serious writers should read About Writing.