Although not exactly along the same lines (Horror, intensity), If you haven't read them before, I would recommend either Robert Ludlum or Clive Cussler.
Both are great authors that can keep you captivated in their stories.
For Ludlum I would recommend reading the Bourne Identity (If you've seen the movie, don't worry, the book is nothing like the movie - 100 times better) it is a great intro into the writing of Robert Ludlum. Lots of plot twists, character developement, intrigue, surprises, etc...
For Cussler I would recommend reading Dragon. Cussler is more of a straight up author. He takes one premise, a super-duper action hero, and revolves his story around the antics and abilities of this Character (Dirk Pitt). Although not as complicated as Ludlum, if you want a good guy winning by doing what good guys do best, then it's hard to beat Cussler.
Another option might be a good Michael Crichton book. He delves more into the scientific thrillers, but he is a great author who knows how to keep you hooked on his stories. Both Jurassic Park (Again, very very different from the movie) and Sphere are two great intro's into his work.
John Grisham is another of my favorite authors. His specialty is the law, and he uses some very colorful characters to tell some really great stories. His book, the FIRM, is a great intro into his work (this book is actually very much like the movie, except the ending).
And finally, I would recommend Tom Clancy. Without a doubt, one of my all-time favorites. He deals mostly with military themes, but he uses some of the best characters to bring across some amazing stories. Patriot Games is a classic example (Again, the book is very different from the movie, although you can't help but picture Harrison Ford's face while reading the book), or, if you want something a little more intense (and longer) from Clancy, try reading WITHOUT REMORSE. The character developement in this story is some of the best I've ever read.