I watched it on Netflix. Here's a trailer:
The Guardian gives it 4 out of 5 stars and opens, "A mind-bending Möbius strip of a movie, this indie sci-fi makes up for what it lacks in budget with a wealth of playful ideas." Wired calls it "masterful"
Roger Ebert's site opens a positive review with this: "If you have a good idea, a strong cast, a smart script, and directorial chops, you don't need a lot of money to make a compelling movie. "The Endless" is proof." Rotten Tomatoes has a critics consensus rating of 93%.