The Elements of Style, now in its fourth edition, is an American English writing style guide originally published in 1918 by Cornell University professor William Strunk Jr. (<--Usually I would put a comma between Strunk and Jr., but I omitted the punctuation as it's not entirely necessary, though commonly practiced). E.B. White, who actually studied under Strunk at Cornell, had forgotten about the "little book" until 1957 when it came to his attention while working at the New Yorker. White wrote a piece praising Strunk for promoting cleanliness, accuracy, and brevity in the use of English and thus was later approached by the publisher to recast a new edition. I purchased the book last week in part because I felt it's something I should have as a writer, especially since I can almost never remember when to use "which" and when to use "that". Given my grades in middle school, especially English, it's a modern marvel that people actually pay me to write at all. I'm not going to lie though, I also bought the book for the Maira Kalman illustrations. You may recognize Kalman's illustrations because many have graced the cover of the New Yorker, one of her more famous ones being "New Yorkistan" from December 2001.
Perhaps the idea of reading a book about grammar doesn't exactly seem like the sexiest way to spend your evening, even with the spectacular illustrations. Below is one of my favorite excerpts, maybe it will persuade you to buy the book.
From chapter four, Words and Expressions Commonly Misused
Flammable. An oddity, chiefly useful in saving lives. The common word meaning "combustible" is inflammable. But some people are thrown off by the in- and think inflammable means "not combustible." For this reason, trucks carrying gasoline or explosives are now marked FLAMMABLE. Unless you are operating such a truck and hence are concerned with the safety of children and illiterates, use inflammable.
You can purchase the Hard Cover edition ($20) or paperback version ($10), both will help you make "every word tell" and both contain Kalman's 57 exquisite illustrations.