It's a pretty good movie, from a great novel.  I definitely don't think of it as a horror film, but you're right that the final sequence is certainly bizarre and horrifying, reminding me of the climactic revelations from SUDDENLY, LAST SUMMER (which is also not a horror film, but probably closer to the mark than LOCUST.)

If you want to know what God thinks of money, just look at the people he gave it to.                                                                                     Dorothy Parker