This brief book can teach the inexpert writer much, and even experts will learn a few new things. However, it presents itself, and is often presented by others, as a flawless masterpiece - something it is not.
What jars most is that the book itself is riddled with errors. I'm not nit-picking about pedantic subtleties - there are real, serious mistakes: the authors spell the English place "Bridgwater" as "Bridgewater", for example, and they often omit essential hyphens, thereby missing their meaning.
I was also upset that so many of the before-and-after examples are flawed. Too often, in mending style, nuances are lost; in many cases I could see alternatives that were more correct, brief, elegant and exact.
It would be interesting to see Strunk's original offering, or an earlier edition of White's adaptation: some of the material is pristine and unobjectionable, so maybe successive editings have let the work fall from former greatness. It is hard to tell, now.
If you are buying just one book on English usage, let it be Bill Bryson's "Troublesome Words". If you want to own a legendary work on the subject, buy Fowler. If you already have a dozen such books, by all means get this one too.