Although Crichton makes it seem, in the book, like this is based on real events, it is fiction. See this Wikipedia entry about “Congo”.
Dr. Karen Ross is in Houston working remotely with a field team from the Earth Resources Technology Services, Inc. (ERTS) in the Congo.
The team is close to their goal of, hopefully, finding valuable, and extremely rare blue, Type IIb, diamonds near the fabled lost city of Zinj in the Congo.
After setting up camp, including a video camera, the field team is wiped out (their heads crushed) by some unknown, very powerful, highly intelligent, gorilla, or, at least, a beast that looks like a gorilla.
Shocked and baffled, Dr. Ross decides to lead her own team into the Congo to find out what happened to this team, and also, to find the diamonds. The only difference this time is Dr. Ross asks noted University of California at Berkeley zoologist and primate researcher, Dr. Peter Elliott and his gorilla, Amy, to come along.
Amy, by the way, can sign over 600 words and is quite intelligent. She also loves to be tickled, “Amy good gorilla”.
“Congo” follows the new team to the Congo as they discover new worlds, new species, and experience the horror of…..the Congo.
This is not Crichton’s best work, but, it is a fun, fast read with lots of interesting, if outdated (the paperback version was published in 1980), technology.
They made a movie with Laura Linney as Dr. Ross. 🙂