I've had pretty good luck by putting in a string of keywords for my favorites. For example, psychological thriller mystery suspense or medical thriller mystery suspense. I think one of the problems is that so many authors put their books under everything in an effort to reach more readers. The other day I was looking for a good legal thriller and found several erotica mixed in there. I hate erotica. Sometimes you'll find vampire books mixed in with mystery. I don't like those either and sometimes download them by mistake.
I shall be watching this thread to see what other suggestions cone up - typing in THRILLERS is no better - there are too many.