A solid, standard horror flick with enough twists and surprises to make it interesting if not brilliant. Del Toro discovered and produced the full-length expansion of this film from a 4 min short (also on the disc). But unlike The Orphanage (another movie he championed), Mama is not nearly as well written or suspenseful. It is based on standard tropes and bad horror-movie logic. Some of it wince-inducing.
Fortunately, the actors manage to mostly overcome the inherent limitations of the script. Coster-Waldau (Game of Thrones) is strong with what little he has. He even gets to play two roles. However, much like the doctor (played by Kash), his motivations and decisions are less than credible by the end. On the other hand, Chastain (Zero Dark Thirty, Take Shelter) gets to try on some new duds, hair, and ink to provide a core and credible performance that is only mildly insulting to women. I don’t say that lightly–they set up her character and her drives at the top, but then it is all undercut by having her main impetus still be external rather than internal (of course she wants to protect the children for her man). Honestly, that was all a bit lazy and unforgivable.
All this aside, you’ll be pulled along and enjoy the visuals and ideas. I particularly give the writers and director credit for resolutions and ultimate messages. This won’t be a classic, but the film makers will certainly be back again; they have something to say and I expect they will get better at it over time.