Like every other aspiring writer, I own several "how-to" books about writing. Some are good for mechanical advice on the process itself; others are good for inspirational purposes (writing is lonely, and kindred spirits are hard to find except in print); and still others are good for placing writing in one's life. Here are a few of my favorite writing books:
Writer's Market (2001 ed.): This book, published yearly, is basically a catalog of markets for various types of writing. It also contains a large number of articles pertaining to writing, including interviews with prominent writers from different genres. A yearly feature is a selection of query letters, some done well and some done (remarkably) badly. The badly-done ones are amazingly instructive.
The Elements of Style by William Strunk Jr. and E. B. White. This brief book is indispensible. It is part-handbook, part-hymn to clarity in writing, part-instruction manual. Its most famous admonition, "Omit needless words", will be (and should be) a mantra for writers.
How To Write Science Fiction and Fantasy by Orson Scott Card. This is an excellent and concise introduction to the problems and pitfalls specific to these two genres. Card is one of the biggest names in SF and he brings all of his expertise to bear. The best part of the book is the section on world-building, a concern of particular (some would say paramount) importance to the SF and Fantasy writer.
Advice to Writers compiled and edited by Jon Winokur. Subtitled "A Compendium of Quotes, Anecdotes, and Writerly Wisdom from a Dazzling Array of Literary Lights", this book is just that: a collection of thoughts on various topics from such people as Woody Allen, Isaac Asimov, Anton Chekhov, William Faulkner, E. B. White, Tennessee Williams....this is a fun book to dip into, for nuggets such as this by William Styron: "You write because you want to be read."
On Writing: A Memoir of the Craft by Stephen King. Given the thickness of many of King's novels and his ability to churn them out at the rate of two per year, one might expect On Writing to be a veritable doorstop. Instead, King writes a fairly brief book that partly relates how writing has shaped his life (and, not unimportantly, how his life has shaped his writing) and partly doles out some of the more important advice from the many writing lessons King has absorbed through the years. The advice section contains nothing that you won't find anywhere else, but somehow the old chestnut "Show, don't tell" seems more vivid when illustrated by King. And you'll certainly never look at adverbs the same way again....but what makes the book so good is King's meditations on writing itself and its place in his life, especially as he describes his problems with alcohol and drug addiction. His life's lesson, learned very late, is this: "Life is not a support system for art. It's the other way around." King later describes, in rather harrowing detail, his recent life-threatening accident when he was struck by a van and his return to health and to writing. It's powerful stuff, and what shines through most is not King's love for writing but his love for his wife, whom he considers his "ideal reader".