I really appreciate that the flick takes its time to build up the suspense. The spooky & shocking effects are used very economically but striking as Hitchcock would have done it. Together with the Mexican cinematographer Antonio Riestra the trio created claustrophobic and surrealistic scenes which reminded me of Luis Buñuel and painters like Salvador Dalí (who cooperated with Buñuel).
"Mama" shows of course a lot of influences, especially from Japanese ghost movies. But I reckon the team developed those ideas further and created a unique piece of spooky art .
Megan Charpentier & Isabelle Nélisse who incarnated the possessed kids were quite amazing and it was a lot of joy the see the gorgeous Jessica Chastain again ("Lawless", "Zero Dark Thirty").
If you like good "old-fashioned" ghost movies "Mama" could make your day.