The Sense of Style: The Thinking Person's Guide to Writing in the 21st Century by Steven Pinker
Like a lot of writers, I'm a sucker for a book that seems as if it'll help me write better.
Thing is, a lot of books that promise this don't really help. In fact some of them seem designed to make me a much worse writer -- stilted, robotic, monotonous, and confused.
While some stylebooks are helpful, even mission-critical for writers, many are a crazed hodge-podge of duh advice ("omit needless words"), grammar myths ("don't split infinitives), and flat-out terrible advice ("never use passive voice"). If you follow that kind of advice, God help you.
(I've ranted elsewhere about the much-loved but mostly destructive Strunk and White stylebook.)
Pinker's book can save you from the stylebook poison. The Sense of Style is kind of an anti-style-book style book. It's about common sense and paying attention to your writing, not following misleading myths and pet peeves of the self-proclaimed grammar mavens:
...incurious about the logic and history of the English language and the ways in which it has been used.... They have a tin ear for its nuances of meaning and emphasis. Too lazy to crack open a dictionary, they are led by gut feeling and intuition rather than attention to careful scholarship. For these writers, language is not a vehicle for clarity and grace but a way to signal their membership in a social clique.
If all this book did was poke grammar Nazis in the eye, I'd recommend it. But it does more than that: It proposed a better way to think about writing. It can help you with anything from word choice to sentence structure to overall coherence.
It can make you a better fundraiser.