I Know What You Did Last Summer, You Killed Mr. Griffin

Has anyone read a Lois Duncan book? They are really freaky. I've only read I Know What You Did Last Summer and Killing Mr. Griffin (hence the title of the post). Both of the books are insanely scary (Mr. Griffin more so). They both have nothing to do with eachother but here's the low-down:

Killing Mr. Griffin: A couple of kids decide to kidnap their english teacher but, (suprise, suprise) he ends up dying because he has a heart problem and they (the kids) destroyed the pills he takes to help him with it. Oddly, Mr. Griffin's death is not the scary part. The aftermath is.

I Know What You Did Last Summer: Four kids were involved in a hit-and-run accident that happened -wait for it- over the summer. They try to forget about it until someone sends a message to one of the people saying -you guessed it- I know what you did last summer. Mr. Griffin is better by far though both of the books are short-200 page books that are good airplane reads because they don't weigh a lot.

I can only imagine how weird Lois Duncan must be to write so scary and vivid books about murder...