I'm looking for a book that will help me with things such as building tension, amping up my horror in horror stories, etc.
Give me books you've read, and that have helped you with your writing. Doesn't matter if the book is geared towards writing sci-fi, fantasy, horror, etc.
I enjoyed Stephen King's In Writing, and I took bits of it here and there that helped me.
The only thing I can think of (and it's not genre based, but overall) is something Utah told me to read. Writing Down the Bones: Freeing the Writer Within She does another one too, I'll have to find it.
It really changed the way I wrote.
Telling Details, Kat Duncan
Writing Scary Scenes, Rayne Hall
Violence: A Writer's Guide, Rory Miller
Rivet Your Readers With Deep Point Of View, Jill Nelson
The last is the shortest. All of this is searchable on Amazon, in the kindle section, which I did before buying, so this selection represents a good many books that were examined and passed over before I ever layed down my hard earned cash. For those books I passed by, the reviews and reader highlighted quotes were scraped for saliency and stored in idea fieldstones ala Weinberg on Writing: The Fieldstone Method that run up to 1500 words apiece and represent the Coles Notes version of books I will never buy or read which saves me hundreds upon hundreds of dollars.
On Writing Horror, ed. Mort Castle
I hear Ray Bradbury's Zen in the Art of Writing is supposed to be good. Probably not as far as learning how to build tension though. I would actually recommend books on screenwriting for that. They're more concerned with stuff like that than books on writing fiction.
Save the Cat offers an interesting perspective; it is for screenwriters, but most of it applies direclty to high concept scripts, which in my mind, equate to genre writing.
^Blake Snyder is the dude that does the "beat sheet," right? That really is a useful outline technique. I love the Screenwriter's Bible as far as script books go. Bradbury's Zen isn't going to have the kind of stuff the op's looking for, though it is just a great book. King's Danse Macabre has some great insights on horror, and seconding Mort Castle.
I have a whole of host of craft writing books on my shelf, and I've gotta tell you, I have yet to read any of them the whole way through (except King's On Writing). I've found that the best way to learn to write is to read novels, short stories, etc. Want to write horror? Devour as much horror as you can. Buy paperback copies and mark them up as if they were textbooks. Highlight, notes, underlining, etc. Then, if you really like the book, buy another copy or pick it up in hardback. I never mark up my hardbacks.
Try reading books outside of the genre you're writing in. Every author has at least on point of craft that they excel in. I always recommend Elmore Leonard for dialogue. Nobody ever believes me when I say this, but Nicholas Sparks is amazing at drawing out tension. Go to Barnes and Noble and pick up his book The Rescue. Read the first chapter, just the first chapter, and you'll see what I mean. Shit, you don't even have to buy the book.
But, if you're hell bent of getting books on craft, my suggestions would be:
1. Character Traits by Linda Edelstein. She gives a rundown on physchologicl, physical, mental, emotional, financial and phyisological attributes of just about every character you can think of. I've found it to be instrumental in my development as a writer.
2. Writing Mysteries by Writers Digest books. Not horror, but a lot of the same ideas and elements contained in it.
3. Writing the Breakout Novel by Donald Maass. More geared towards finished manuscripts (there's a workbook that goes along with the book, too) but there are some great nuggets of information in there. The perspective of the book comes from a verteran literary agent. Great, great stuff.
4. On Writing by King. You've read it. In my opinion, the best book about the craft. Hands down.
Aside from that, and this is just my opinion, the rest just rehash what the others said. You're better off reading novels. That's the best way I've found to learn.
One more.
The First Five Pages by Noah Lukeman. Great book on how to grab your readers/publishers in the first five pages.
Follow Donald Maass's twitter, he does these "tips for a first manuscript" or something like that, which are great.
I have a Twitter account, but I never use it. I hear it's a good platform for writers, though. I'll check out his Twitter (uh, whatever they call them. Posts, I guess?)
The one craft book I refer to continually is Architectures of Possiblility, After Innovative Writing by Lance Olsen and Trevor Dodge.
Not so much specific to genre as essential to non shit fiction. It's amazing, amazing.
http://moodywriting.blogspot.com/ --- Simple, actionable advice (which, if I'm honest, I don't really employ; but the posts make sense when I read them.)
Tweets, you twitter tweets.