There’s little doubt Michael Crichton was an absolute master of science fiction and medical thrillers.

In a literary career spanning more than four decades, the best-selling author sold over 200 million copies of his novels worldwide—and that doesn’t even touch on his success as a screenwriter, director, and producer of films and television.

From the longest running primetime medical drama in American history (ER) to the movie that inspired HBO’s new hit series Westworld, Michael Crichton had a hand in some of the best science fiction of the late 20^th century both on and off the page.

But we’re not here to talk about Crichton the director and screenwriter—we’re here to talk about the novelist of contemporary science fiction thrillers that have placed his name amongst the best sci-fi authors of all time.

It’s hard to pick favorites, but most lists require it. Here are my top 5 recommended Michael Crichton books you simply can’t afford to miss.

Jurassic Park

When a bestselling book makes the leap to film, every devout bibliophile claims the book was better. And in many cases, they’re right. Michael Crichton’s cautionary tale about genetic engineering gone wrong weaves a much creepier story on paper than what ended up on the big screen.

Just take the novel’s primary antagonist, John Hammond. In the book, the owner of Jurassic Park and founder of parent company InGen is a rather loathsome proprietor; his only interest lying in making a profit while caring little for his fellow man—or women, or his own grandkids for that matter.

In the movies, however, Hammond is kind, jovial, and the grandfather every dinosaur-crazy grandkid would love to visit during the summer. And he’s played by Sir Richard Attenborough . . . how could you not like that guy? Dude was Kris Kringle, for crying out loud.

Other notable differences include a handful of exhilarating scenes in the novel that were likely left out of the first movie for time, but made it to the cinematic sequels. These include the famous T. rex waterfall scene, a journey through the pterodactyl aviary, and a handful of character deaths that didn’t transfer to film. (My favorite character, Muldoon, lives in the book, but the biggest badass on Isla Nublar dies on screen? Total crock of shit, Spielberg.)

Sphere

I doubt Crichton’s work is ever compared to that of M. Night Shamalan’s, but when it comes to a twist ending, Sphere doesn’t disappoint.

This one starts out with all the right ingredients for a thrilling oceanic-themed sci-fi yarn. A team of scientists is called in to investigate the wreckage of an unknown spacecraft that’s been discovered by the U.S. Navy at the bottom of the Pacific Ocean. Sounds like an underwater version of Roswell, New Mexico, until the team realizes the spacecraft has nothing to do with little green men and weather balloons.

This is where the story gets really interesting. Not only is it determined that the spacecraft was made in the U.S.A. some time in the future, it’s also revealed that the spacecraft was in contact with an unknown alien entity—a fact that could point to a dismal fate for the research team involved.

I don’t want to give away too much for obvious reasons. But when it comes to the ending—particularly how the scientists are going to get back to the surface alive—you won’t see it coming. And that makes it an excellent thriller worth seeing through to the very last page.

Take my word for it: This one’s worth it just for the twist.

Congo

Another Crichton book-turned-blockbuster, Congo is a fast-paced story where primal instinct faces off against modern weaponry in a battle for the most valuable diamonds known to man—and ape.

Readers are instantly immersed a mysterious storyline involving a failed expedition to the Virunga region of the Congo. A team searching for a rare tech-industry-disrupting diamond is attacked and killed by an unknown race of grey-haired gorillas that were bred millennia ago to protect the Lost City of Zinj.

From there, the action doesn’t stop. The failure of the initial mission leads to reinforcements returning to the Congo, with tech-company competitors sending their own teams in a race for the most valuable diamonds in the world.

What they find once they reach the Lost City of Zinj is sure to blow away sci-fi fans, especially those who would enjoy a story that explores how intelligent life in the animal kingdom could give human beings a run for their money.

The Andromeda Strain

This one is a great example of just how far ahead of his time Crichton’s stories were. Published in 1969, the book follows a team of scientists investigating a crashed satellite in Arizona that brought back a few microscopic hitchhikers from outer space.

In other words, the space plague visits the southwest, and scientists work feverishly to keep it from becoming a full-blown civilization-ending epidemic the likes of which the world has never seen.

The Andromeda Strain does a great job of showcasing Crichton’s medical and scientific expertise. From genetic mutations that keep the mysterious space bug one step ahead of the team, to people who are exposed to the bug but are miraculously unaffected, Crichton leads readers through different scenarios that are more than plausible and backed up by real science—something that makes this story even creepier.

I don’t want to give too much away, but if you’re a fan of medical sci-fi thrillers, then this one is a must-read.

The Terminal Man

This one ranks pretty low on most lists highlighting Crichton’s best work, but this is my list, so I’m making a case for it.

The story follows a violent epileptic patient who is the subject of an experimental procedure that may cure his condition. The procedure involves implanting electrodes into the mind of the patient, Harry Benson, in the hopes that electric shocks delivered to different regions of his brain may neutralize his violent outbreaks during epileptic episodes.

What gets the reader emotionally invested in the story is the fact that Benson can’t remember these violent episodes. Rather, he’s horrified once his seizures come to an end and he’s informed about what he’s done. This makes (most) readers feel for the guy, and also begs a thought-provoking question: If you had a mental illness, how far would you go to cure it?

A handful of doctors are also involved in the procedure, and their differing viewpoints give Crichton the platform needed to explore whether controlling the mind—regardless of the intention–is morally responsible, or a step too far (Think Mary Shelley’s Frankenstein). I’ve always loved science fiction that calls into question the ethics behind new technology and its applications, and in that regard The Terminal Man doesn’t disappoint.

That wraps up my list of Crichton’s Top 5. Do you agree with the works cited, or did I leave one of your favorite Crichton novels off the list? Feel free to drop me a line in the comments section below.