Without going into detail--because, you know, I can't do that, what with NDAs and the flesh-eating mutant grub-soldiers that Wizards uses to enforce those NDAs...
I can say that
Heroes of Horror should add to almost any horror D&D game you're running. It focuses on different types, and different aspects, of horror. So yes, there's advice for "creepy, don't know what's going on, jump when you hear a noise" horror, advice for "we're trapped in a confined area with limited supplies and something's eating us" horror, and of course advice for, "DEARHEAVENWHATISTHATOHGODITSEATINGMYFACE!!!!" horror.
I'd say more, but I really can't. The fact that it discusses multiple types of horror is in the printed catalog, so I know it's not secret. Beyond that, all I can promise is, when I'm allowed to say more, I definitely will. Heck, I'm excited; this is my first WotC gig after four+ years in the industry, so when I'm allowed to say more, you probaby won't be able to shut me the hell up.