Ed and Lorraine Warren are 30-year veterans of the demonology wars: they helped investigate the Amityville case, along with about three thousand others, and they've got heaps to communicate (as calmly as you please) about what demons are and aren't. For one thing, they're not ghosts; those are mostly poor aimless souls who haven't quite figured out that they're dead yet. No, the genuine article is an inhuman spirit in league with the hierarchy of devils (Lucifer et al.) and given to screaming obscenities and exuding odors of excrement. Sometimes these ""bastards,"" as Ed so neatly puts it, utterly possess their victims; sometimes they're content to wreak havoc with poltergeist antics. Characteristically, though, they don't start up with people unless they have some sort of permission; cases of misplaced curiosity about Ouija boards and conjuring tricks are cited as warning. Typically, the Warrens live in a state of danger that would intimidate a seasoned spy: their cars are forever veering off the road or being bombarded by foul stuff on the way back from another successful demon-rout. And thank goodness for holy water; that, along with finger tracings of crosses in the air, saved the dynamic duo more than once, as black cloud masses advanced and threatened to materialize in their midst. Most of this is the Warrens' home-grown theory (there are fallen angels, after all), interspersed with enough scary stories to keep exorcism fans writhing. But the real horror here is that the Warrens make it all sound so downright reasonable--weren't they called on by the general at West Point to collar a ghost?--that they may stir up more interest and experimentation with the occult. Troubling.