Cut-Rate Alien knock-off, if the crew never got off LV-426 and it starred Ferris Bueller's father and Francine from American Dad. It's sort of amazing it can crib fully wholesale from such a seminal film and still exist. And it does it so badly to boot!
Hostel meets The Happening, as tourists run afoul of, well..(Spoiler: it's killer vines). Given the story, The Ruins is not a ridiculous as it could have been. Some queasy moments here and there, but in a more visceral way (lots of battlefield surgery) than genuine suspense. Not as obnoxious as it could have been, but not as effective as it should be (by all accounts, the book is a tense read)
Despite a great opening act (with some wonderful skewering of Hollywood) and a decent climax, there's a full hour in the middle that drags on and on. The occasional funny riff will keep you watching, but this is the kind of movie that makes a great trailer, was probably a blast to make, but not so much fun to watch.