Writing Fiction by the Faculty of Gotham Writers' Workshop and edited by Alexander Steele, is what I consider the most complete writing how-to I've found out there, and it's the guide I've most often recommended or handed out to writers at all stages of the game who want to better understand the major elements of story. It's not Novel Writing 101 in a book, and like most scholarly books on writing written by teachers it suffers from a literary skew, but it does a very decent job of explaining theory and the big basics, and it offers some interesting exercises to apply what you've read about in each section.
Other writers swear by Robert McKee's Story, which I've read, but it's a book of story theory for screenwriters, and you have to adapt everything in it to apply it to novels (which isn't a bad thing; you could do a lot worse than learning about story from a screenwriter.)
While I've been scouring the how-to aisles for years in search of better, I haven't yet found it. Most of the authors who write how-tos are either not working novelists, or have very limited practical experience. The few that I've read authored by veteran working writers (Stephen King would be a shining example of this) were mainly memoirs dressed up as how-tos. Interesting as they can be, they're more about the author's particular journey to superstardom, which I don't think is practical or especially applicable to the average novelist.
I can't read everything, so I know I've probably missed some good soup-to-nuts how-tos out there, and I wanted to ask you guys for some recommendations. If you could have only one book about novel writing in your reference collection, what would it be? Let me know in comments by midnight EST on Monday, May 7, 2012. I will draw one name at random from everyone who participates and grant the winner a BookWish*. This giveaway is open to everyone on the planet, even if you've won something here at PBW in the past.
*A BookWish is any book of your choice that is available for order from an online bookseller, up to maximum cost of $30.00 U.S. I will throw in any applicable shipping charges involved.