On Writing Horror from the Horror Writer's Association is one of the best books regarding horror writing I've read in years. However, most book's on writing have lots of good advice that can be applied to horror writing specifically and in general.
Overall, if it's a good technique or idea in any other genre, it's a good idea to crossover and use in horror.
Suspense, intrigue, plot, mystery, characterization, drama, all of these are things which are basically universal to all writing genres.
The most useful books of all are Strunk & White's, a good dictionary, and a good thesaurus. Everything else is gravy.