I read the original book version of this movie back in 2014. I liked it and it earned four stars on Goodreads, and this past weekend I found the movie was now available on Hulu, so I threw it on.
I was very pleasantly surprised.
Movies based on books seem to be very hit or miss. Most of them take characters and a few major scenes, and then leave out some important details, while making up other parts that were never in the book.
I think I'm getting ahead of myself though.
FAIR WARNING! SPOILERS BELOW!
The Ruins is about a group of young 20-somethings, coming up on the end of their trip to Mexico. They meet a few others, and someone produces an old, hand-drawn map to some local ruins. They head out, and the map ends up being correct. As they get there though, they become cornered by a group of locals who suddenly prevent them from leaving.
Left with nowhere to go, they head deeper into the ruins, discovering the remains of an archaeological expedition. Injuries mount as they explore, until they discover the vines covering the structure are hungry for blood. The vines themselves creep along, mimicking sounds they want to hear, grabbing, stabbing into their wounds, devouring them alive. With nowhere to go and a hungry enemy closing in, they turn on each other, until only a few remain.
The last two, a couple, devise a plan to get her away past the natives. It works, and she escapes, while her boyfriend pays for the plan with his life.
Now, as I was saying, this movie follows the book pretty damn closely! Closer than any other adaptation I've ever read. Of course, a lot of details are left out in order to cram the main story into the time allowed. The Ruins is no different in that, however, they leave in enough small details that if you've read the book, you won't be disappointed.
There is a single, major difference from the book though, the girl's escape, potentially spreading the spores. I'm not sure how I feel about that. It sets up a sequel, to be certain, but the way the natives had the entire ruin surrounded, I'm not sure how much I believe the boyfriend's simple distraction would have worked.
Regardless. The movie is well made, with lots of tension, believable characters that you like, and a realistic enough scenario. If you like horror, this should be near the top of movies to see. It might not be a classic in the usual sense, but given time, it may become one.