The Elements of Style does not deserve the enormous esteem in which it is held by American college graduates. Its advice ranges from limp platitudes to inconsistent nonsense. Its enormous influence has not improved American students’ grasp of English grammar; it has significantly degraded it.
That is linguistics professor Geoffrey Pullum writing in The Chronicle Review. He makes many pointed points and, most damning, shows a striking number of mistakes and contradiction.
But I always loved Strunk & White, and still do. So long as you don’t read it like a rule book, but know when and where to break the rules, you are fine. “Knowing the rules and then breaking them” is probably as good a description of excellent writing as I can manage.
What else to read? On Writing Well, more than any book, probably had the most influence on my style. Writing Tools is by no means profound, but has some helpful bits. The author’s more recent book, The Glamour of Grammar is pretty much useless.
I remain surprised that writers and journalists everywhere seem to celebrate Stephen King’s On Writing. I have been intrigued enough to buy it, but not yet intrigued enough to read it.
Finally, if you’re into really inexpert and doubtful advice, see my own advice on essay writing.