I Know What You Did Last Summer Book vs Movie Review

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**Warning: Spoilers for both book and movie!**

I Know What You Did Last Summer by Lois Duncan (1973)

I Know What You Did Last Summer directed by Jim Gillespie (1997)

Welcome to October! To kick off Halloween month, I decided to cover what has become a classic slasher 90’s movie. The book is by Lois Duncan and when I was in junior high and high school, I read all her books the library had! She is great at writing young adult thrillers. As you will soon learn, the book is not a “slasher” story at all and is quite different!

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Literally everyone is familiar with the premise of this story. Four teenagers hit someone while driving and leave them to die. They make a pact never to talk of it again. One year later, they get a message saying, “I know what you did last summer.” Which ensues a mystery as to who knows about the accidental murder.

Thoughts on the Book

As I said, when I was in my early teens, I loved Loid Duncan books. Now that about 15 years has passed, I can’t say re-reading this makes me want to re-read any of her others. It’s well written and has a fun twist, but I think it is just a better fit for a younger audience.

Having said that, I did enjoy this story. It has also become kind of iconic, so clearly, she had something here.

The version I read this time around is an updated one that was released in 2010. She made it applicable to todays readers by adding in cell phones, email, texting, and swapping the Vietnam war for Iraq. I was not a fan of this. I enjoy reading books from different time periods because it gives you a feel for what things were like then. I know this isn’t a period piece, and 1973 wasn’t that long ago. Nonetheless, I still enjoy putting myself in the shoes of those in a different time and by updating it, this aspect was lost.


I of course had watched this movie before and remembered it quite well despite it having been so long ago! There is a sequel (which isn’t based on a book) but even though I enjoyed this movie pretty well back in the day, I have never gotten around to watching the second one. Kevin Williamson wrote the script for this, but nobody wanted to make the movie because they felt that slasher movies we no longer popular. He then wrote Scream, which he was able to get made into a movie. With the success of that, slasher movies were “in” again! Especially slasher movies with a comedic element to them.


The cast list basically screams “late 90’s”.

Jennifer Love Hewitt plays Julie. She has said she isn’t a fan of the horror genre and this and its sequel are the only scary movies she has been in. I think she’s an alright actress in this. There is a line at the end of the movie between her and Ray though that is delivered so terribly. This is a teen slasher movie though so you can’t be expecting Oscar worthy performances. She was the youngest cast member, being only 18 in this movie!

Sarah Michelle Gellar is Helen and I thought she did a better job than Hewitt actually. She of course went on to star in Buffy the Vampire Slayer, which I have never seen though I’ve heard great things.

Ryan Phillipe is well cast as the annoying jock Barry. His then girlfriend Reese Witherspoon auditioned for this movie, but then decided to withdraw. However, she recommended Phillipe for the role of Barry!

Freddie Prinze Jr plays the kind, yet suspicious Ray. He and Gellar started dating while working on this movie and are still together to this day!

Hit and Run

In the movie, it isn’t a hit and run. They hit the fisherman on the road, and then they stop to check on him. They think he is dead are going to toss him into the ocean. When they do, he grabs them, but they still end up tossing him in. In some ways it’s better that they stopped, but then it just turns to full on murder.

In the book, they hit a young boy who is on his bicycle. Barry is driving, in the movie it’s Ray, and he keeps going. They call 911, but by then it’s been over ten minutes since they hit him. They read in the paper that the boy died while he was in the ambulance on the way to the hospital.

I know what you did

In the movie, the guy they hit is the one that comes back and harasses them. In the book, the boy they hit had a brother who was deployed at the time of the death. When he comes back to the states, it’s been some time since and so he is upset that he missed spending time with his little brother and missed the funeral. He lives at their home with his sister and starts dating Julie. He pretends to just so happen to see her in the library and starts talking to her. Later, he moves into the same building Helen is staying and starts a sort of friendship with her.

Ray comes back in town and hears about his guy Julie has started seeing and meets up with him briefly. Ray realizes it is the dead boy’s brother and he is the one that pieces it together in time.

In the book, Barry is shot in the stomach, however he does live. He is just hospital bound for the rest of the book. Helen is threatened by the brother and he reveals who he is. She gets away from him by jumping out her window on the second floor but survives. In the movie, Barry is hit by a car and is in the hospital but is released soon. He is later killed. Helen is being chased by the fisherman and jumps out of a window like in the book. However, she too ultimately is killed. Her sister Elsa is also killed in the movie. In both book and movie, Elsa is shown to not be very nice and in the book, Julie even suspects she might be involved, but nothing really happens with her.

Changes to Characters

Starting with Julie. In the movie when we meet Julie before the incident, she is made out to be a straight A student. In the book, she had been much more into cheerleading and various extracurricular activities. After the accident though, she becomes very studious and that becomes her focus. Also, in the movie they have all graduated. In the book only Barry and Ray had graduated. Helen and Julie still had another year of school.

In the movie, before the incident, Helen was crowned “Croaker Queen”, which doesn’t really mean much, I guess. She plans to go to New York and begin her acting career. However, she instead stays living at home and works with her sister Elsa at their family store. In the book, I think it was soon after the accident, or maybe right before, she submits her photo to the local news station and wins the title “Future Five Star”. She then drops out of school after her junior year and works for the channel five news station. She is getting paid well and can get an apartment at a swanky building. She seems not to be bothered about what they did and is moving forward with her life and living well.

She and Barry stay together. He was impressed how she was on his side after the hit and run, and then she became Future Five Star, and it would have been foolish to dump a girl who is now on the news and has a posh apartment. He does cheat on her though. We also see into their home lives. Barry, as we see in the movie comes from a rich family. His mother doesn’t approve of Helen, who comes from a poor family. The movie just shows her dad and Elsa. But in the book her mom and dad are both around and they have like six kids.

Julie’s mom in the book has this sixth sense kind of thing, where she can feel when something is wrong. The night of the hit and run, she gets it really strong, but then Julie is home at a decent time and things appear to be fine.

Ray has probably the smallest role in the movie, but that is partly because they want us to suspect him. In the book, Julie, Barry and Helen briefly mention it could have been Ray who sent to the note, but nothing further.

Visiting Missy

In the movie, Helen and Julie go visit Missy, the relative of the person they think they killed. Julie also goes to visit a second time. In both, the sister seems kind of off, and you get an eerie feeling.

In the book, Julie and Ray go. When they visit her, the sister is very nice and chatty. In both, we learn that the mom is somewhere else in a home because the death of her son was so hard on her. In the book it isn’t creepy at all, but Julie feels terrible knowing all the pain they caused from that night.

Lois Duncan’s Opinion of Movie

Author Lois Duncan actually had nothing to do with the making of the movie and said, “The movie was a shock to me…it was very exciting to learn that it was going to be a major motion picture. I could hardly wait to see it…I thought, “That is my book, but who is that man and what is he going to do with that ice hook?” Well, I soon found out. He was going to decapitate my characters…I was so horrified…It was quite a shocker.”

As far as her involvement in the movie, she said, “They kept me as far away as possible. I think they were afraid of how I might react if I realized what my little masterpiece was going to turn into.” She also went on to say, “I had expected it to be my story, but it wasn’t. It was my characters and my plot gimmick, but then it went in all directions. Even the double identity twist, which was the crux of the story, had been omitted. Also, I was quite horrified by the sensationalized violence. Several years earlier my own daughter, Kait, had been chased down in her car and shot to death, and I had seen, right in front of my eyes, what real violence is. To have people screaming and laughing about it did not go down well.”

Clearly, Duncan does not like the movie. But there is the plus side because thanks to that movie, her book sales went up like crazy! And four decades later her books are still getting published.

Book or Movie

This movie has pretty bad ratings online, however, I still enjoyed it for nostalgic reasons. Is it a top rate thriller though? No, though when I watched it when I was younger, I seem to remember being much more pulled in and even suspected Ray.

The book, as I said, is targeting a younger audience, so it too isn’t the best thriller I’ve read. But as I said, when I was in my teens I loved her books! In the end, I think I would still go with the book being better. It’s a thriller/mystery and isn’t gory. Then there’s that twist at the end when we find out the guy who was behind it all.